dm raid: fix restoring of failed devices regression

[deliverable/linux.git] / drivers / md / dm-raid.c

/*
 * Copyright (C) 2010-2011 Neil Brown
 * Copyright (C) 2010-2016 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the GPL.
 */

#include <linux/slab.h>
#include <linux/module.h>

#include "md.h"
#include "raid1.h"
#include "raid5.h"
#include "raid10.h"
#include "bitmap.h"

#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "raid"
#define MAX_RAID_DEVICES        253 /* md-raid kernel limit */

/*
 * Minimum sectors of free reshape space per raid device
 */
#define MIN_FREE_RESHAPE_SPACE to_sector(4*4096)

static bool devices_handle_discard_safely = false;

/*
 * The following flags are used by dm-raid.c to set up the array state.
 * They must be cleared before md_run is called.
 */
#define FirstUse 10             /* rdev flag */

struct raid_dev {
        /*
         * Two DM devices, one to hold metadata and one to hold the
         * actual data/parity.  The reason for this is to not confuse
         * ti->len and give more flexibility in altering size and
         * characteristics.
         *
         * While it is possible for this device to be associated
         * with a different physical device than the data_dev, it
         * is intended for it to be the same.
         *    |--------- Physical Device ---------|
         *    |- meta_dev -|------ data_dev ------|
         */
        struct dm_dev *meta_dev;
        struct dm_dev *data_dev;
        struct md_rdev rdev;
};

/*
 * Bits for establishing rs->ctr_flags
 *
 * 1 = no flag value
 * 2 = flag with value
 */
#define __CTR_FLAG_SYNC                 0  /* 1 */ /* Not with raid0! */
#define __CTR_FLAG_NOSYNC               1  /* 1 */ /* Not with raid0! */
#define __CTR_FLAG_REBUILD              2  /* 2 */ /* Not with raid0! */
#define __CTR_FLAG_DAEMON_SLEEP         3  /* 2 */ /* Not with raid0! */
#define __CTR_FLAG_MIN_RECOVERY_RATE    4  /* 2 */ /* Not with raid0! */
#define __CTR_FLAG_MAX_RECOVERY_RATE    5  /* 2 */ /* Not with raid0! */
#define __CTR_FLAG_MAX_WRITE_BEHIND     6  /* 2 */ /* Only with raid1! */
#define __CTR_FLAG_WRITE_MOSTLY         7  /* 2 */ /* Only with raid1! */
#define __CTR_FLAG_STRIPE_CACHE         8  /* 2 */ /* Only with raid4/5/6! */
#define __CTR_FLAG_REGION_SIZE          9  /* 2 */ /* Not with raid0! */
#define __CTR_FLAG_RAID10_COPIES        10 /* 2 */ /* Only with raid10 */
#define __CTR_FLAG_RAID10_FORMAT        11 /* 2 */ /* Only with raid10 */
/* New for v1.9.0 */
#define __CTR_FLAG_DELTA_DISKS          12 /* 2 */ /* Only with reshapable raid1/4/5/6/10! */
#define __CTR_FLAG_DATA_OFFSET          13 /* 2 */ /* Only with reshapable raid4/5/6/10! */
#define __CTR_FLAG_RAID10_USE_NEAR_SETS 14 /* 2 */ /* Only with raid10! */

/*
 * Flags for rs->ctr_flags field.
 */
#define CTR_FLAG_SYNC                   (1 << __CTR_FLAG_SYNC)
#define CTR_FLAG_NOSYNC                 (1 << __CTR_FLAG_NOSYNC)
#define CTR_FLAG_REBUILD                (1 << __CTR_FLAG_REBUILD)
#define CTR_FLAG_DAEMON_SLEEP           (1 << __CTR_FLAG_DAEMON_SLEEP)
#define CTR_FLAG_MIN_RECOVERY_RATE      (1 << __CTR_FLAG_MIN_RECOVERY_RATE)
#define CTR_FLAG_MAX_RECOVERY_RATE      (1 << __CTR_FLAG_MAX_RECOVERY_RATE)
#define CTR_FLAG_MAX_WRITE_BEHIND       (1 << __CTR_FLAG_MAX_WRITE_BEHIND)
#define CTR_FLAG_WRITE_MOSTLY           (1 << __CTR_FLAG_WRITE_MOSTLY)
#define CTR_FLAG_STRIPE_CACHE           (1 << __CTR_FLAG_STRIPE_CACHE)
#define CTR_FLAG_REGION_SIZE            (1 << __CTR_FLAG_REGION_SIZE)
#define CTR_FLAG_RAID10_COPIES          (1 << __CTR_FLAG_RAID10_COPIES)
#define CTR_FLAG_RAID10_FORMAT          (1 << __CTR_FLAG_RAID10_FORMAT)
#define CTR_FLAG_DELTA_DISKS            (1 << __CTR_FLAG_DELTA_DISKS)
#define CTR_FLAG_DATA_OFFSET            (1 << __CTR_FLAG_DATA_OFFSET)
#define CTR_FLAG_RAID10_USE_NEAR_SETS   (1 << __CTR_FLAG_RAID10_USE_NEAR_SETS)

/*
 * Definitions of various constructor flags to
 * be used in checks of valid / invalid flags
 * per raid level.
 */
/* Define all any sync flags */
#define CTR_FLAGS_ANY_SYNC              (CTR_FLAG_SYNC | CTR_FLAG_NOSYNC)

/* Define flags for options without argument (e.g. 'nosync') */
#define CTR_FLAG_OPTIONS_NO_ARGS        (CTR_FLAGS_ANY_SYNC | \
                                         CTR_FLAG_RAID10_USE_NEAR_SETS)

/* Define flags for options with one argument (e.g. 'delta_disks +2') */
#define CTR_FLAG_OPTIONS_ONE_ARG (CTR_FLAG_REBUILD | \
                                  CTR_FLAG_WRITE_MOSTLY | \
                                  CTR_FLAG_DAEMON_SLEEP | \
                                  CTR_FLAG_MIN_RECOVERY_RATE | \
                                  CTR_FLAG_MAX_RECOVERY_RATE | \
                                  CTR_FLAG_MAX_WRITE_BEHIND | \
                                  CTR_FLAG_STRIPE_CACHE | \
                                  CTR_FLAG_REGION_SIZE | \
                                  CTR_FLAG_RAID10_COPIES | \
                                  CTR_FLAG_RAID10_FORMAT | \
                                  CTR_FLAG_DELTA_DISKS | \
                                  CTR_FLAG_DATA_OFFSET)

/* Valid options definitions per raid level... */

/* "raid0" does only accept data offset */
#define RAID0_VALID_FLAGS       (CTR_FLAG_DATA_OFFSET)

/* "raid1" does not accept stripe cache, data offset, delta_disks or any raid10 options */
#define RAID1_VALID_FLAGS       (CTR_FLAGS_ANY_SYNC | \
                                 CTR_FLAG_REBUILD | \
                                 CTR_FLAG_WRITE_MOSTLY | \
                                 CTR_FLAG_DAEMON_SLEEP | \
                                 CTR_FLAG_MIN_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_WRITE_BEHIND | \
                                 CTR_FLAG_REGION_SIZE | \
                                 CTR_FLAG_DELTA_DISKS | \
                                 CTR_FLAG_DATA_OFFSET)

/* "raid10" does not accept any raid1 or stripe cache options */
#define RAID10_VALID_FLAGS      (CTR_FLAGS_ANY_SYNC | \
                                 CTR_FLAG_REBUILD | \
                                 CTR_FLAG_DAEMON_SLEEP | \
                                 CTR_FLAG_MIN_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_RECOVERY_RATE | \
                                 CTR_FLAG_REGION_SIZE | \
                                 CTR_FLAG_RAID10_COPIES | \
                                 CTR_FLAG_RAID10_FORMAT | \
                                 CTR_FLAG_DELTA_DISKS | \
                                 CTR_FLAG_DATA_OFFSET | \
                                 CTR_FLAG_RAID10_USE_NEAR_SETS)

/*
 * "raid4/5/6" do not accept any raid1 or raid10 specific options
 *
 * "raid6" does not accept "nosync", because it is not guaranteed
 * that both parity and q-syndrome are being written properly with
 * any writes
 */
#define RAID45_VALID_FLAGS      (CTR_FLAGS_ANY_SYNC | \
                                 CTR_FLAG_REBUILD | \
                                 CTR_FLAG_DAEMON_SLEEP | \
                                 CTR_FLAG_MIN_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_WRITE_BEHIND | \
                                 CTR_FLAG_STRIPE_CACHE | \
                                 CTR_FLAG_REGION_SIZE | \
                                 CTR_FLAG_DELTA_DISKS | \
                                 CTR_FLAG_DATA_OFFSET)

#define RAID6_VALID_FLAGS       (CTR_FLAG_SYNC | \
                                 CTR_FLAG_REBUILD | \
                                 CTR_FLAG_DAEMON_SLEEP | \
                                 CTR_FLAG_MIN_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_RECOVERY_RATE | \
                                 CTR_FLAG_MAX_WRITE_BEHIND | \
                                 CTR_FLAG_STRIPE_CACHE | \
                                 CTR_FLAG_REGION_SIZE | \
                                 CTR_FLAG_DELTA_DISKS | \
                                 CTR_FLAG_DATA_OFFSET)
/* ...valid options definitions per raid level */

/*
 * Flags for rs->runtime_flags field
 * (RT_FLAG prefix meaning "runtime flag")
 *
 * These are all internal and used to define runtime state,
 * e.g. to prevent another resume from preresume processing
 * the raid set all over again.
 */
#define RT_FLAG_RS_PRERESUMED           0
#define RT_FLAG_RS_RESUMED              1
#define RT_FLAG_RS_BITMAP_LOADED        2
#define RT_FLAG_UPDATE_SBS              3
#define RT_FLAG_RESHAPE_RS              4

/* Array elements of 64 bit needed for rebuild/failed disk bits */
#define DISKS_ARRAY_ELEMS ((MAX_RAID_DEVICES + (sizeof(uint64_t) * 8 - 1)) / sizeof(uint64_t) / 8)

/*
 * raid set level, layout and chunk sectors backup/restore
 */
struct rs_layout {
        int new_level;
        int new_layout;
        int new_chunk_sectors;
};

struct raid_set {
        struct dm_target *ti;

        uint32_t bitmap_loaded;
        uint32_t stripe_cache_entries;
        unsigned long ctr_flags;
        unsigned long runtime_flags;

        uint64_t rebuild_disks[DISKS_ARRAY_ELEMS];

        int raid_disks;
        int delta_disks;
        int data_offset;
        int raid10_copies;
        int requested_bitmap_chunk_sectors;

        struct mddev md;
        struct raid_type *raid_type;
        struct dm_target_callbacks callbacks;

        struct raid_dev dev[0];
};

static void rs_config_backup(struct raid_set *rs, struct rs_layout *l)
{
        struct mddev *mddev = &rs->md;

        l->new_level = mddev->new_level;
        l->new_layout = mddev->new_layout;
        l->new_chunk_sectors = mddev->new_chunk_sectors;
}

static void rs_config_restore(struct raid_set *rs, struct rs_layout *l)
{
        struct mddev *mddev = &rs->md;

        mddev->new_level = l->new_level;
        mddev->new_layout = l->new_layout;
        mddev->new_chunk_sectors = l->new_chunk_sectors;
}

/* raid10 algorithms (i.e. formats) */
#define ALGORITHM_RAID10_DEFAULT        0
#define ALGORITHM_RAID10_NEAR           1
#define ALGORITHM_RAID10_OFFSET         2
#define ALGORITHM_RAID10_FAR            3

/* Supported raid types and properties. */
static struct raid_type {
        const char *name;               /* RAID algorithm. */
        const char *descr;              /* Descriptor text for logging. */
        const unsigned int parity_devs; /* # of parity devices. */
        const unsigned int minimal_devs;/* minimal # of devices in set. */
        const unsigned int level;       /* RAID level. */
        const unsigned int algorithm;   /* RAID algorithm. */
} raid_types[] = {
        {"raid0",         "raid0 (striping)",                       0, 2, 0,  0 /* NONE */},
        {"raid1",         "raid1 (mirroring)",                      0, 2, 1,  0 /* NONE */},
        {"raid10_far",    "raid10 far (striped mirrors)",           0, 2, 10, ALGORITHM_RAID10_FAR},
        {"raid10_offset", "raid10 offset (striped mirrors)",        0, 2, 10, ALGORITHM_RAID10_OFFSET},
        {"raid10_near",   "raid10 near (striped mirrors)",          0, 2, 10, ALGORITHM_RAID10_NEAR},
        {"raid10",        "raid10 (striped mirrors)",               0, 2, 10, ALGORITHM_RAID10_DEFAULT},
        {"raid4",         "raid4 (dedicated last parity disk)",     1, 2, 4,  ALGORITHM_PARITY_N}, /* raid4 layout = raid5_n */
        {"raid5_n",       "raid5 (dedicated last parity disk)",     1, 2, 5,  ALGORITHM_PARITY_N},
        {"raid5_ls",      "raid5 (left symmetric)",                 1, 2, 5,  ALGORITHM_LEFT_SYMMETRIC},
        {"raid5_rs",      "raid5 (right symmetric)",                1, 2, 5,  ALGORITHM_RIGHT_SYMMETRIC},
        {"raid5_la",      "raid5 (left asymmetric)",                1, 2, 5,  ALGORITHM_LEFT_ASYMMETRIC},
        {"raid5_ra",      "raid5 (right asymmetric)",               1, 2, 5,  ALGORITHM_RIGHT_ASYMMETRIC},
        {"raid6_zr",      "raid6 (zero restart)",                   2, 4, 6,  ALGORITHM_ROTATING_ZERO_RESTART},
        {"raid6_nr",      "raid6 (N restart)",                      2, 4, 6,  ALGORITHM_ROTATING_N_RESTART},
        {"raid6_nc",      "raid6 (N continue)",                     2, 4, 6,  ALGORITHM_ROTATING_N_CONTINUE},
        {"raid6_n_6",     "raid6 (dedicated parity/Q n/6)",         2, 4, 6,  ALGORITHM_PARITY_N_6},
        {"raid6_ls_6",    "raid6 (left symmetric dedicated Q 6)",   2, 4, 6,  ALGORITHM_LEFT_SYMMETRIC_6},
        {"raid6_rs_6",    "raid6 (right symmetric dedicated Q 6)",  2, 4, 6,  ALGORITHM_RIGHT_SYMMETRIC_6},
        {"raid6_la_6",    "raid6 (left asymmetric dedicated Q 6)",  2, 4, 6,  ALGORITHM_LEFT_ASYMMETRIC_6},
        {"raid6_ra_6",    "raid6 (right asymmetric dedicated Q 6)", 2, 4, 6,  ALGORITHM_RIGHT_ASYMMETRIC_6}
};

/* True, if @v is in inclusive range [@min, @max] */
static bool __within_range(long v, long min, long max)
{
        return v >= min && v <= max;
}

/* All table line arguments are defined here */
static struct arg_name_flag {
        const unsigned long flag;
        const char *name;
} __arg_name_flags[] = {
        { CTR_FLAG_SYNC, "sync"},
        { CTR_FLAG_NOSYNC, "nosync"},
        { CTR_FLAG_REBUILD, "rebuild"},
        { CTR_FLAG_DAEMON_SLEEP, "daemon_sleep"},
        { CTR_FLAG_MIN_RECOVERY_RATE, "min_recovery_rate"},
        { CTR_FLAG_MAX_RECOVERY_RATE, "max_recovery_rate"},
        { CTR_FLAG_MAX_WRITE_BEHIND, "max_write_behind"},
        { CTR_FLAG_WRITE_MOSTLY, "write_mostly"},
        { CTR_FLAG_STRIPE_CACHE, "stripe_cache"},
        { CTR_FLAG_REGION_SIZE, "region_size"},
        { CTR_FLAG_RAID10_COPIES, "raid10_copies"},
        { CTR_FLAG_RAID10_FORMAT, "raid10_format"},
        { CTR_FLAG_DATA_OFFSET, "data_offset"},
        { CTR_FLAG_DELTA_DISKS, "delta_disks"},
        { CTR_FLAG_RAID10_USE_NEAR_SETS, "raid10_use_near_sets"},
};

/* Return argument name string for given @flag */
static const char *dm_raid_arg_name_by_flag(const uint32_t flag)
{
        if (hweight32(flag) == 1) {
                struct arg_name_flag *anf = __arg_name_flags + ARRAY_SIZE(__arg_name_flags);

                while (anf-- > __arg_name_flags)
                        if (flag & anf->flag)
                                return anf->name;

        } else
                DMERR("%s called with more than one flag!", __func__);

        return NULL;
}

/*
 * Bool helpers to test for various raid levels of a raid set.
 * It's level as reported by the superblock rather than
 * the requested raid_type passed to the constructor.
 */
/* Return true, if raid set in @rs is raid0 */
static bool rs_is_raid0(struct raid_set *rs)
{
        return !rs->md.level;
}

/* Return true, if raid set in @rs is raid1 */
static bool rs_is_raid1(struct raid_set *rs)
{
        return rs->md.level == 1;
}

/* Return true, if raid set in @rs is raid10 */
static bool rs_is_raid10(struct raid_set *rs)
{
        return rs->md.level == 10;
}

/* Return true, if raid set in @rs is level 6 */
static bool rs_is_raid6(struct raid_set *rs)
{
        return rs->md.level == 6;
}

/* Return true, if raid set in @rs is level 4, 5 or 6 */
static bool rs_is_raid456(struct raid_set *rs)
{
        return __within_range(rs->md.level, 4, 6);
}

/* Return true, if raid set in @rs is reshapable */
static bool __is_raid10_far(int layout);
static bool rs_is_reshapable(struct raid_set *rs)
{
        return rs_is_raid456(rs) ||
               (rs_is_raid10(rs) && !__is_raid10_far(rs->md.new_layout));
}

/* Return true, if raid set in @rs is recovering */
static bool rs_is_recovering(struct raid_set *rs)
{
        return rs->md.recovery_cp < rs->dev[0].rdev.sectors;
}

/* Return true, if raid set in @rs is reshaping */
static bool rs_is_reshaping(struct raid_set *rs)
{
        return rs->md.reshape_position != MaxSector;
}

/*
 * bool helpers to test for various raid levels of a raid type @rt
 */

/* Return true, if raid type in @rt is raid0 */
static bool rt_is_raid0(struct raid_type *rt)
{
        return !rt->level;
}

/* Return true, if raid type in @rt is raid1 */
static bool rt_is_raid1(struct raid_type *rt)
{
        return rt->level == 1;
}

/* Return true, if raid type in @rt is raid10 */
static bool rt_is_raid10(struct raid_type *rt)
{
        return rt->level == 10;
}

/* Return true, if raid type in @rt is raid4/5 */
static bool rt_is_raid45(struct raid_type *rt)
{
        return __within_range(rt->level, 4, 5);
}

/* Return true, if raid type in @rt is raid6 */
static bool rt_is_raid6(struct raid_type *rt)
{
        return rt->level == 6;
}

/* Return true, if raid type in @rt is raid4/5/6 */
static bool rt_is_raid456(struct raid_type *rt)
{
        return __within_range(rt->level, 4, 6);
}
/* END: raid level bools */

/* Return valid ctr flags for the raid level of @rs */
static unsigned long __valid_flags(struct raid_set *rs)
{
        if (rt_is_raid0(rs->raid_type))
                return RAID0_VALID_FLAGS;
        else if (rt_is_raid1(rs->raid_type))
                return RAID1_VALID_FLAGS;
        else if (rt_is_raid10(rs->raid_type))
                return RAID10_VALID_FLAGS;
        else if (rt_is_raid45(rs->raid_type))
                return RAID45_VALID_FLAGS;
        else if (rt_is_raid6(rs->raid_type))
                return RAID6_VALID_FLAGS;

        return 0;
}

/*
 * Check for valid flags set on @rs
 *
 * Has to be called after parsing of the ctr flags!
 */
static int rs_check_for_valid_flags(struct raid_set *rs)
{
        if (rs->ctr_flags & ~__valid_flags(rs)) {
                rs->ti->error = "Invalid flags combination";
                return -EINVAL;
        }

        return 0;
}

/* MD raid10 bit definitions and helpers */
#define RAID10_OFFSET                   (1 << 16) /* stripes with data copies area adjacent on devices */
#define RAID10_BROCKEN_USE_FAR_SETS     (1 << 17) /* Broken in raid10.c: use sets instead of whole stripe rotation */
#define RAID10_USE_FAR_SETS             (1 << 18) /* Use sets instead of whole stripe rotation */
#define RAID10_FAR_COPIES_SHIFT         8         /* raid10 # far copies shift (2nd byte of layout) */

/* Return md raid10 near copies for @layout */
static unsigned int __raid10_near_copies(int layout)
{
        return layout & 0xFF;
}

/* Return md raid10 far copies for @layout */
static unsigned int __raid10_far_copies(int layout)
{
        return __raid10_near_copies(layout >> RAID10_FAR_COPIES_SHIFT);
}

/* Return true if md raid10 offset for @layout */
static bool __is_raid10_offset(int layout)
{
        return !!(layout & RAID10_OFFSET);
}

/* Return true if md raid10 near for @layout */
static bool __is_raid10_near(int layout)
{
        return !__is_raid10_offset(layout) && __raid10_near_copies(layout) > 1;
}

/* Return true if md raid10 far for @layout */
static bool __is_raid10_far(int layout)
{
        return !__is_raid10_offset(layout) && __raid10_far_copies(layout) > 1;
}

/* Return md raid10 layout string for @layout */
static const char *raid10_md_layout_to_format(int layout)
{
        /*
         * Bit 16 stands for "offset"
         * (i.e. adjacent stripes hold copies)
         *
         * Refer to MD's raid10.c for details
         */
        if (__is_raid10_offset(layout))
                return "offset";

        if (__raid10_near_copies(layout) > 1)
                return "near";

        WARN_ON(__raid10_far_copies(layout) < 2);

        return "far";
}

/* Return md raid10 algorithm for @name */
static int raid10_name_to_format(const char *name)
{
        if (!strcasecmp(name, "near"))
                return ALGORITHM_RAID10_NEAR;
        else if (!strcasecmp(name, "offset"))
                return ALGORITHM_RAID10_OFFSET;
        else if (!strcasecmp(name, "far"))
                return ALGORITHM_RAID10_FAR;

        return -EINVAL;
}

/* Return md raid10 copies for @layout */
static unsigned int raid10_md_layout_to_copies(int layout)
{
        return max(__raid10_near_copies(layout), __raid10_far_copies(layout));
}

/* Return md raid10 format id for @format string */
static int raid10_format_to_md_layout(struct raid_set *rs,
                                      unsigned int algorithm,
                                      unsigned int copies)
{
        unsigned int n = 1, f = 1, r = 0;

        /*
         * MD resilienece flaw:
         *
         * enabling use_far_sets for far/offset formats causes copies
         * to be colocated on the same devs together with their origins!
         *
         * -> disable it for now in the definition above
         */
        if (algorithm == ALGORITHM_RAID10_DEFAULT ||
            algorithm == ALGORITHM_RAID10_NEAR)
                n = copies;

        else if (algorithm == ALGORITHM_RAID10_OFFSET) {
                f = copies;
                r = RAID10_OFFSET;
                if (!test_bit(__CTR_FLAG_RAID10_USE_NEAR_SETS, &rs->ctr_flags))
                        r |= RAID10_USE_FAR_SETS;

        } else if (algorithm == ALGORITHM_RAID10_FAR) {
                f = copies;
                r = !RAID10_OFFSET;
                if (!test_bit(__CTR_FLAG_RAID10_USE_NEAR_SETS, &rs->ctr_flags))
                        r |= RAID10_USE_FAR_SETS;

        } else
                return -EINVAL;

        return r | (f << RAID10_FAR_COPIES_SHIFT) | n;
}
/* END: MD raid10 bit definitions and helpers */

/* Check for any of the raid10 algorithms */
static bool __got_raid10(struct raid_type *rtp, const int layout)
{
        if (rtp->level == 10) {
                switch (rtp->algorithm) {
                case ALGORITHM_RAID10_DEFAULT:
                case ALGORITHM_RAID10_NEAR:
                        return __is_raid10_near(layout);
                case ALGORITHM_RAID10_OFFSET:
                        return __is_raid10_offset(layout);
                case ALGORITHM_RAID10_FAR:
                        return __is_raid10_far(layout);
                default:
                        break;
                }
        }

        return false;
}

/* Return raid_type for @name */
static struct raid_type *get_raid_type(const char *name)
{
        struct raid_type *rtp = raid_types + ARRAY_SIZE(raid_types);

        while (rtp-- > raid_types)
                if (!strcasecmp(rtp->name, name))
                        return rtp;

        return NULL;
}

/* Return raid_type for @name based derived from @level and @layout */
static struct raid_type *get_raid_type_by_ll(const int level, const int layout)
{
        struct raid_type *rtp = raid_types + ARRAY_SIZE(raid_types);

        while (rtp-- > raid_types) {
                /* RAID10 special checks based on @layout flags/properties */
                if (rtp->level == level &&
                    (__got_raid10(rtp, layout) || rtp->algorithm == layout))
                        return rtp;
        }

        return NULL;
}

/*
 * Conditionally change bdev capacity of @rs
 * in case of a disk add/remove reshape
 */
static void rs_set_capacity(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;
        struct md_rdev *rdev;
        struct gendisk *gendisk = dm_disk(dm_table_get_md(rs->ti->table));

        /*
         * raid10 sets rdev->sector to the device size, which
         * is unintended in case of out-of-place reshaping
         */
        rdev_for_each(rdev, mddev)
                rdev->sectors = mddev->dev_sectors;

        set_capacity(gendisk, mddev->array_sectors);
        revalidate_disk(gendisk);
}

/*
 * Set the mddev properties in @rs to the current
 * ones retrieved from the freshest superblock
 */
static void rs_set_cur(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;

        mddev->new_level = mddev->level;
        mddev->new_layout = mddev->layout;
        mddev->new_chunk_sectors = mddev->chunk_sectors;
}

/*
 * Set the mddev properties in @rs to the new
 * ones requested by the ctr
 */
static void rs_set_new(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;

        mddev->level = mddev->new_level;
        mddev->layout = mddev->new_layout;
        mddev->chunk_sectors = mddev->new_chunk_sectors;
        mddev->raid_disks = rs->raid_disks;
        mddev->delta_disks = 0;
}

static struct raid_set *raid_set_alloc(struct dm_target *ti, struct raid_type *raid_type,
                                       unsigned int raid_devs)
{
        unsigned int i;
        struct raid_set *rs;

        if (raid_devs <= raid_type->parity_devs) {
                ti->error = "Insufficient number of devices";
                return ERR_PTR(-EINVAL);
        }

        rs = kzalloc(sizeof(*rs) + raid_devs * sizeof(rs->dev[0]), GFP_KERNEL);
        if (!rs) {
                ti->error = "Cannot allocate raid context";
                return ERR_PTR(-ENOMEM);
        }

        mddev_init(&rs->md);

        rs->raid_disks = raid_devs;
        rs->delta_disks = 0;

        rs->ti = ti;
        rs->raid_type = raid_type;
        rs->stripe_cache_entries = 256;
        rs->md.raid_disks = raid_devs;
        rs->md.level = raid_type->level;
        rs->md.new_level = rs->md.level;
        rs->md.layout = raid_type->algorithm;
        rs->md.new_layout = rs->md.layout;
        rs->md.delta_disks = 0;
        rs->md.recovery_cp = MaxSector;

        for (i = 0; i < raid_devs; i++)
                md_rdev_init(&rs->dev[i].rdev);

        /*
         * Remaining items to be initialized by further RAID params:
         *  rs->md.persistent
         *  rs->md.external
         *  rs->md.chunk_sectors
         *  rs->md.new_chunk_sectors
         *  rs->md.dev_sectors
         */

        return rs;
}

static void raid_set_free(struct raid_set *rs)
{
        int i;

        for (i = 0; i < rs->raid_disks; i++) {
                if (rs->dev[i].meta_dev)
                        dm_put_device(rs->ti, rs->dev[i].meta_dev);
                md_rdev_clear(&rs->dev[i].rdev);
                if (rs->dev[i].data_dev)
                        dm_put_device(rs->ti, rs->dev[i].data_dev);
        }

        kfree(rs);
}

/*
 * For every device we have two words
 *  <meta_dev>: meta device name or '-' if missing
 *  <data_dev>: data device name or '-' if missing
 *
 * The following are permitted:
 *    - -
 *    - <data_dev>
 *    <meta_dev> <data_dev>
 *
 * The following is not allowed:
 *    <meta_dev> -
 *
 * This code parses those words.  If there is a failure,
 * the caller must use raid_set_free() to unwind the operations.
 */
static int parse_dev_params(struct raid_set *rs, struct dm_arg_set *as)
{
        int i;
        int rebuild = 0;
        int metadata_available = 0;
        int r = 0;
        const char *arg;

        /* Put off the number of raid devices argument to get to dev pairs */
        arg = dm_shift_arg(as);
        if (!arg)
                return -EINVAL;

        for (i = 0; i < rs->raid_disks; i++) {
                rs->dev[i].rdev.raid_disk = i;

                rs->dev[i].meta_dev = NULL;
                rs->dev[i].data_dev = NULL;

                /*
                 * There are no offsets, since there is a separate device
                 * for data and metadata.
                 */
                rs->dev[i].rdev.data_offset = 0;
                rs->dev[i].rdev.mddev = &rs->md;

                arg = dm_shift_arg(as);
                if (!arg)
                        return -EINVAL;

                if (strcmp(arg, "-")) {
                        r = dm_get_device(rs->ti, arg, dm_table_get_mode(rs->ti->table),
                                          &rs->dev[i].meta_dev);
                        if (r) {
                                rs->ti->error = "RAID metadata device lookup failure";
                                return r;
                        }

                        rs->dev[i].rdev.sb_page = alloc_page(GFP_KERNEL);
                        if (!rs->dev[i].rdev.sb_page) {
                                rs->ti->error = "Failed to allocate superblock page";
                                return -ENOMEM;
                        }
                }

                arg = dm_shift_arg(as);
                if (!arg)
                        return -EINVAL;

                if (!strcmp(arg, "-")) {
                        if (!test_bit(In_sync, &rs->dev[i].rdev.flags) &&
                            (!rs->dev[i].rdev.recovery_offset)) {
                                rs->ti->error = "Drive designated for rebuild not specified";
                                return -EINVAL;
                        }

                        if (rs->dev[i].meta_dev) {
                                rs->ti->error = "No data device supplied with metadata device";
                                return -EINVAL;
                        }

                        continue;
                }

                r = dm_get_device(rs->ti, arg, dm_table_get_mode(rs->ti->table),
                                  &rs->dev[i].data_dev);
                if (r) {
                        rs->ti->error = "RAID device lookup failure";
                        return r;
                }

                if (rs->dev[i].meta_dev) {
                        metadata_available = 1;
                        rs->dev[i].rdev.meta_bdev = rs->dev[i].meta_dev->bdev;
                }
                rs->dev[i].rdev.bdev = rs->dev[i].data_dev->bdev;
                list_add_tail(&rs->dev[i].rdev.same_set, &rs->md.disks);
                if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
                        rebuild++;
        }

        if (metadata_available) {
                rs->md.external = 0;
                rs->md.persistent = 1;
                rs->md.major_version = 2;
        } else if (rebuild && !rs->md.recovery_cp) {
                /*
                 * Without metadata, we will not be able to tell if the array
                 * is in-sync or not - we must assume it is not.  Therefore,
                 * it is impossible to rebuild a drive.
                 *
                 * Even if there is metadata, the on-disk information may
                 * indicate that the array is not in-sync and it will then
                 * fail at that time.
                 *
                 * User could specify 'nosync' option if desperate.
                 */
                rs->ti->error = "Unable to rebuild drive while array is not in-sync";
                return -EINVAL;
        }

        return 0;
}

/*
 * validate_region_size
 * @rs
 * @region_size:  region size in sectors.  If 0, pick a size (4MiB default).
 *
 * Set rs->md.bitmap_info.chunksize (which really refers to 'region size').
 * Ensure that (ti->len/region_size < 2^21) - required by MD bitmap.
 *
 * Returns: 0 on success, -EINVAL on failure.
 */
static int validate_region_size(struct raid_set *rs, unsigned long region_size)
{
        unsigned long min_region_size = rs->ti->len / (1 << 21);

        if (!region_size) {
                /*
                 * Choose a reasonable default.  All figures in sectors.
                 */
                if (min_region_size > (1 << 13)) {
                        /* If not a power of 2, make it the next power of 2 */
                        region_size = roundup_pow_of_two(min_region_size);
                        DMINFO("Choosing default region size of %lu sectors",
                               region_size);
                } else {
                        DMINFO("Choosing default region size of 4MiB");
                        region_size = 1 << 13; /* sectors */
                }
        } else {
                /*
                 * Validate user-supplied value.
                 */
                if (region_size > rs->ti->len) {
                        rs->ti->error = "Supplied region size is too large";
                        return -EINVAL;
                }

                if (region_size < min_region_size) {
                        DMERR("Supplied region_size (%lu sectors) below minimum (%lu)",
                              region_size, min_region_size);
                        rs->ti->error = "Supplied region size is too small";
                        return -EINVAL;
                }

                if (!is_power_of_2(region_size)) {
                        rs->ti->error = "Region size is not a power of 2";
                        return -EINVAL;
                }

                if (region_size < rs->md.chunk_sectors) {
                        rs->ti->error = "Region size is smaller than the chunk size";
                        return -EINVAL;
                }
        }

        /*
         * Convert sectors to bytes.
         */
        rs->md.bitmap_info.chunksize = to_bytes(region_size);

        return 0;
}

/*
 * validate_raid_redundancy
 * @rs
 *
 * Determine if there are enough devices in the array that haven't
 * failed (or are being rebuilt) to form a usable array.
 *
 * Returns: 0 on success, -EINVAL on failure.
 */
static int validate_raid_redundancy(struct raid_set *rs)
{
        unsigned int i, rebuild_cnt = 0;
        unsigned int rebuilds_per_group = 0, copies;
        unsigned int group_size, last_group_start;

        for (i = 0; i < rs->md.raid_disks; i++)
                if (!test_bit(In_sync, &rs->dev[i].rdev.flags) ||
                    !rs->dev[i].rdev.sb_page)
                        rebuild_cnt++;

        switch (rs->raid_type->level) {
        case 1:
                if (rebuild_cnt >= rs->md.raid_disks)
                        goto too_many;
                break;
        case 4:
        case 5:
        case 6:
                if (rebuild_cnt > rs->raid_type->parity_devs)
                        goto too_many;
                break;
        case 10:
                copies = raid10_md_layout_to_copies(rs->md.new_layout);
                if (rebuild_cnt < copies)
                        break;

                /*
                 * It is possible to have a higher rebuild count for RAID10,
                 * as long as the failed devices occur in different mirror
                 * groups (i.e. different stripes).
                 *
                 * When checking "near" format, make sure no adjacent devices
                 * have failed beyond what can be handled.  In addition to the
                 * simple case where the number of devices is a multiple of the
                 * number of copies, we must also handle cases where the number
                 * of devices is not a multiple of the number of copies.
                 * E.g.    dev1 dev2 dev3 dev4 dev5
                 *          A    A    B    B    C
                 *          C    D    D    E    E
                 */
                if (__is_raid10_near(rs->md.new_layout)) {
                        for (i = 0; i < rs->md.raid_disks; i++) {
                                if (!(i % copies))
                                        rebuilds_per_group = 0;
                                if ((!rs->dev[i].rdev.sb_page ||
                                    !test_bit(In_sync, &rs->dev[i].rdev.flags)) &&
                                    (++rebuilds_per_group >= copies))
                                        goto too_many;
                        }
                        break;
                }

                /*
                 * When checking "far" and "offset" formats, we need to ensure
                 * that the device that holds its copy is not also dead or
                 * being rebuilt.  (Note that "far" and "offset" formats only
                 * support two copies right now.  These formats also only ever
                 * use the 'use_far_sets' variant.)
                 *
                 * This check is somewhat complicated by the need to account
                 * for arrays that are not a multiple of (far) copies.  This
                 * results in the need to treat the last (potentially larger)
                 * set differently.
                 */
                group_size = (rs->md.raid_disks / copies);
                last_group_start = (rs->md.raid_disks / group_size) - 1;
                last_group_start *= group_size;
                for (i = 0; i < rs->md.raid_disks; i++) {
                        if (!(i % copies) && !(i > last_group_start))
                                rebuilds_per_group = 0;
                        if ((!rs->dev[i].rdev.sb_page ||
                             !test_bit(In_sync, &rs->dev[i].rdev.flags)) &&
                            (++rebuilds_per_group >= copies))
                                        goto too_many;
                }
                break;
        default:
                if (rebuild_cnt)
                        return -EINVAL;
        }

        return 0;

too_many:
        return -EINVAL;
}

/*
 * Possible arguments are...
 *      <chunk_size> [optional_args]
 *
 * Argument definitions
 *    <chunk_size>                      The number of sectors per disk that
 *                                      will form the "stripe"
 *    [[no]sync]                        Force or prevent recovery of the
 *                                      entire array
 *    [rebuild <idx>]                   Rebuild the drive indicated by the index
 *    [daemon_sleep <ms>]               Time between bitmap daemon work to
 *                                      clear bits
 *    [min_recovery_rate <kB/sec/disk>] Throttle RAID initialization
 *    [max_recovery_rate <kB/sec/disk>] Throttle RAID initialization
 *    [write_mostly <idx>]              Indicate a write mostly drive via index
 *    [max_write_behind <sectors>]      See '-write-behind=' (man mdadm)
 *    [stripe_cache <sectors>]          Stripe cache size for higher RAIDs
 *    [region_size <sectors>]           Defines granularity of bitmap
 *
 * RAID10-only options:
 *    [raid10_copies <# copies>]        Number of copies.  (Default: 2)
 *    [raid10_format <near|far|offset>] Layout algorithm.  (Default: near)
 */
static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
                             unsigned int num_raid_params)
{
        int value, raid10_format = ALGORITHM_RAID10_DEFAULT;
        unsigned int raid10_copies = 2;
        unsigned int i, write_mostly = 0;
        unsigned int region_size = 0;
        sector_t max_io_len;
        const char *arg, *key;
        struct raid_dev *rd;
        struct raid_type *rt = rs->raid_type;

        arg = dm_shift_arg(as);
        num_raid_params--; /* Account for chunk_size argument */

        if (kstrtoint(arg, 10, &value) < 0) {
                rs->ti->error = "Bad numerical argument given for chunk_size";
                return -EINVAL;
        }

        /*
         * First, parse the in-order required arguments
         * "chunk_size" is the only argument of this type.
         */
        if (rt_is_raid1(rt)) {
                if (value)
                        DMERR("Ignoring chunk size parameter for RAID 1");
                value = 0;
        } else if (!is_power_of_2(value)) {
                rs->ti->error = "Chunk size must be a power of 2";
                return -EINVAL;
        } else if (value < 8) {
                rs->ti->error = "Chunk size value is too small";
                return -EINVAL;
        }

        rs->md.new_chunk_sectors = rs->md.chunk_sectors = value;

        /*
         * We set each individual device as In_sync with a completed
         * 'recovery_offset'.  If there has been a device failure or
         * replacement then one of the following cases applies:
         *
         *   1) User specifies 'rebuild'.
         *      - Device is reset when param is read.
         *   2) A new device is supplied.
         *      - No matching superblock found, resets device.
         *   3) Device failure was transient and returns on reload.
         *      - Failure noticed, resets device for bitmap replay.
         *   4) Device hadn't completed recovery after previous failure.
         *      - Superblock is read and overrides recovery_offset.
         *
         * What is found in the superblocks of the devices is always
         * authoritative, unless 'rebuild' or '[no]sync' was specified.
         */
        for (i = 0; i < rs->raid_disks; i++) {
                set_bit(In_sync, &rs->dev[i].rdev.flags);
                rs->dev[i].rdev.recovery_offset = MaxSector;
        }

        /*
         * Second, parse the unordered optional arguments
         */
        for (i = 0; i < num_raid_params; i++) {
                key = dm_shift_arg(as);
                if (!key) {
                        rs->ti->error = "Not enough raid parameters given";
                        return -EINVAL;
                }

                if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_NOSYNC))) {
                        if (test_and_set_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags)) {
                                rs->ti->error = "Only one 'nosync' argument allowed";
                                return -EINVAL;
                        }
                        continue;
                }
                if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_SYNC))) {
                        if (test_and_set_bit(__CTR_FLAG_SYNC, &rs->ctr_flags)) {
                                rs->ti->error = "Only one 'sync' argument allowed";
                                return -EINVAL;
                        }
                        continue;
                }
                if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_RAID10_USE_NEAR_SETS))) {
                        if (test_and_set_bit(__CTR_FLAG_RAID10_USE_NEAR_SETS, &rs->ctr_flags)) {
                                rs->ti->error = "Only one 'raid10_use_new_sets' argument allowed";
                                return -EINVAL;
                        }
                        continue;
                }

                arg = dm_shift_arg(as);
                i++; /* Account for the argument pairs */
                if (!arg) {
                        rs->ti->error = "Wrong number of raid parameters given";
                        return -EINVAL;
                }

                /*
                 * Parameters that take a string value are checked here.
                 */

                if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_RAID10_FORMAT))) {
                        if (test_and_set_bit(__CTR_FLAG_RAID10_FORMAT, &rs->ctr_flags)) {
                                rs->ti->error = "Only one 'raid10_format' argument pair allowed";
                                return -EINVAL;
                        }
                        if (!rt_is_raid10(rt)) {
                                rs->ti->error = "'raid10_format' is an invalid parameter for this RAID type";
                                return -EINVAL;
                        }
                        raid10_format = raid10_name_to_format(arg);
                        if (raid10_format < 0) {
                                rs->ti->error = "Invalid 'raid10_format' value given";
                                return raid10_format;
                        }
                        continue;
                }

                if (kstrtoint(arg, 10, &value) < 0) {
                        rs->ti->error = "Bad numerical argument given in raid params";
                        return -EINVAL;
                }

                if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_REBUILD))) {
                        /*
                         * "rebuild" is being passed in by userspace to provide
                         * indexes of replaced devices and to set up additional
                         * devices on raid level takeover.
                         */
                        if (!__within_range(value, 0, rs->raid_disks - 1)) {
                                rs->ti->error = "Invalid rebuild index given";
                                return -EINVAL;
                        }

                        if (test_and_set_bit(value, (void *) rs->rebuild_disks)) {
                                rs->ti->error = "rebuild for this index already given";
                                return -EINVAL;
                        }

                        rd = rs->dev + value;
                        clear_bit(In_sync, &rd->rdev.flags);
                        clear_bit(Faulty, &rd->rdev.flags);
                        rd->rdev.recovery_offset = 0;
                        set_bit(__CTR_FLAG_REBUILD, &rs->ctr_flags);
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_WRITE_MOSTLY))) {
                        if (!rt_is_raid1(rt)) {
                                rs->ti->error = "write_mostly option is only valid for RAID1";
                                return -EINVAL;
                        }

                        if (!__within_range(value, 0, rs->md.raid_disks - 1)) {
                                rs->ti->error = "Invalid write_mostly index given";
                                return -EINVAL;
                        }

                        write_mostly++;
                        set_bit(WriteMostly, &rs->dev[value].rdev.flags);
                        set_bit(__CTR_FLAG_WRITE_MOSTLY, &rs->ctr_flags);
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_MAX_WRITE_BEHIND))) {
                        if (!rt_is_raid1(rt)) {
                                rs->ti->error = "max_write_behind option is only valid for RAID1";
                                return -EINVAL;
                        }

                        if (test_and_set_bit(__CTR_FLAG_MAX_WRITE_BEHIND, &rs->ctr_flags)) {
                                rs->ti->error = "Only one max_write_behind argument pair allowed";
                                return -EINVAL;
                        }

                        /*
                         * In device-mapper, we specify things in sectors, but
                         * MD records this value in kB
                         */
                        value /= 2;
                        if (value > COUNTER_MAX) {
                                rs->ti->error = "Max write-behind limit out of range";
                                return -EINVAL;
                        }

                        rs->md.bitmap_info.max_write_behind = value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_DAEMON_SLEEP))) {
                        if (test_and_set_bit(__CTR_FLAG_DAEMON_SLEEP, &rs->ctr_flags)) {
                                rs->ti->error = "Only one daemon_sleep argument pair allowed";
                                return -EINVAL;
                        }
                        if (!value || (value > MAX_SCHEDULE_TIMEOUT)) {
                                rs->ti->error = "daemon sleep period out of range";
                                return -EINVAL;
                        }
                        rs->md.bitmap_info.daemon_sleep = value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_DATA_OFFSET))) {
                        /* Userspace passes new data_offset after having extended the the data image LV */
                        if (test_and_set_bit(__CTR_FLAG_DATA_OFFSET, &rs->ctr_flags)) {
                                rs->ti->error = "Only one data_offset argument pair allowed";
                                return -EINVAL;
                        }
                        /* Ensure sensible data offset */
                        if (value < 0 ||
                            (value && (value < MIN_FREE_RESHAPE_SPACE || value % to_sector(PAGE_SIZE)))) {
                                rs->ti->error = "Bogus data_offset value";
                                return -EINVAL;
                        }
                        rs->data_offset = value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_DELTA_DISKS))) {
                        /* Define the +/-# of disks to add to/remove from the given raid set */
                        if (test_and_set_bit(__CTR_FLAG_DELTA_DISKS, &rs->ctr_flags)) {
                                rs->ti->error = "Only one delta_disks argument pair allowed";
                                return -EINVAL;
                        }
                        /* Ensure MAX_RAID_DEVICES and raid type minimal_devs! */
                        if (!__within_range(abs(value), 1, MAX_RAID_DEVICES - rt->minimal_devs)) {
                                rs->ti->error = "Too many delta_disk requested";
                                return -EINVAL;
                        }

                        rs->delta_disks = value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_STRIPE_CACHE))) {
                        if (test_and_set_bit(__CTR_FLAG_STRIPE_CACHE, &rs->ctr_flags)) {
                                rs->ti->error = "Only one stripe_cache argument pair allowed";
                                return -EINVAL;
                        }

                        if (!rt_is_raid456(rt)) {
                                rs->ti->error = "Inappropriate argument: stripe_cache";
                                return -EINVAL;
                        }

                        rs->stripe_cache_entries = value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_MIN_RECOVERY_RATE))) {
                        if (test_and_set_bit(__CTR_FLAG_MIN_RECOVERY_RATE, &rs->ctr_flags)) {
                                rs->ti->error = "Only one min_recovery_rate argument pair allowed";
                                return -EINVAL;
                        }
                        if (value > INT_MAX) {
                                rs->ti->error = "min_recovery_rate out of range";
                                return -EINVAL;
                        }
                        rs->md.sync_speed_min = (int)value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_MAX_RECOVERY_RATE))) {
                        if (test_and_set_bit(__CTR_FLAG_MAX_RECOVERY_RATE, &rs->ctr_flags)) {
                                rs->ti->error = "Only one max_recovery_rate argument pair allowed";
                                return -EINVAL;
                        }
                        if (value > INT_MAX) {
                                rs->ti->error = "max_recovery_rate out of range";
                                return -EINVAL;
                        }
                        rs->md.sync_speed_max = (int)value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_REGION_SIZE))) {
                        if (test_and_set_bit(__CTR_FLAG_REGION_SIZE, &rs->ctr_flags)) {
                                rs->ti->error = "Only one region_size argument pair allowed";
                                return -EINVAL;
                        }

                        region_size = value;
                        rs->requested_bitmap_chunk_sectors = value;
                } else if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_RAID10_COPIES))) {
                        if (test_and_set_bit(__CTR_FLAG_RAID10_COPIES, &rs->ctr_flags)) {
                                rs->ti->error = "Only one raid10_copies argument pair allowed";
                                return -EINVAL;
                        }

                        if (!__within_range(value, 2, rs->md.raid_disks)) {
                                rs->ti->error = "Bad value for 'raid10_copies'";
                                return -EINVAL;
                        }

                        raid10_copies = value;
                } else {
                        DMERR("Unable to parse RAID parameter: %s", key);
                        rs->ti->error = "Unable to parse RAID parameter";
                        return -EINVAL;
                }
        }

        if (test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags) &&
            test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags)) {
                rs->ti->error = "sync and nosync are mutually exclusive";
                return -EINVAL;
        }

        if (test_bit(__CTR_FLAG_REBUILD, &rs->ctr_flags) &&
            (test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags) ||
             test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags))) {
                rs->ti->error = "sync/nosync and rebuild are mutually exclusive";
                return -EINVAL;
        }

        if (write_mostly >= rs->md.raid_disks) {
                rs->ti->error = "Can't set all raid1 devices to write_mostly";
                return -EINVAL;
        }

        if (validate_region_size(rs, region_size))
                return -EINVAL;

        if (rs->md.chunk_sectors)
                max_io_len = rs->md.chunk_sectors;
        else
                max_io_len = region_size;

        if (dm_set_target_max_io_len(rs->ti, max_io_len))
                return -EINVAL;

        if (rt_is_raid10(rt)) {
                if (raid10_copies > rs->md.raid_disks) {
                        rs->ti->error = "Not enough devices to satisfy specification";
                        return -EINVAL;
                }

                rs->md.new_layout = raid10_format_to_md_layout(rs, raid10_format, raid10_copies);
                if (rs->md.new_layout < 0) {
                        rs->ti->error = "Error getting raid10 format";
                        return rs->md.new_layout;
                }

                rt = get_raid_type_by_ll(10, rs->md.new_layout);
                if (!rt) {
                        rs->ti->error = "Failed to recognize new raid10 layout";
                        return -EINVAL;
                }

                if ((rt->algorithm == ALGORITHM_RAID10_DEFAULT ||
                     rt->algorithm == ALGORITHM_RAID10_NEAR) &&
                    test_bit(__CTR_FLAG_RAID10_USE_NEAR_SETS, &rs->ctr_flags)) {
                        rs->ti->error = "RAID10 format 'near' and 'raid10_use_near_sets' are incompatible";
                        return -EINVAL;
                }
        }

        rs->raid10_copies = raid10_copies;

        /* Assume there are no metadata devices until the drives are parsed */
        rs->md.persistent = 0;
        rs->md.external = 1;

        /* Check, if any invalid ctr arguments have been passed in for the raid level */
        return rs_check_for_valid_flags(rs);
}

/* Set raid4/5/6 cache size */
static int rs_set_raid456_stripe_cache(struct raid_set *rs)
{
        int r;
        struct r5conf *conf;
        struct mddev *mddev = &rs->md;
        uint32_t min_stripes = max(mddev->chunk_sectors, mddev->new_chunk_sectors) / 2;
        uint32_t nr_stripes = rs->stripe_cache_entries;

        if (!rt_is_raid456(rs->raid_type)) {
                rs->ti->error = "Inappropriate raid level; cannot change stripe_cache size";
                return -EINVAL;
        }

        if (nr_stripes < min_stripes) {
                DMINFO("Adjusting requested %u stripe cache entries to %u to suit stripe size",
                       nr_stripes, min_stripes);
                nr_stripes = min_stripes;
        }

        conf = mddev->private;
        if (!conf) {
                rs->ti->error = "Cannot change stripe_cache size on inactive RAID set";
                return -EINVAL;
        }

        /* Try setting number of stripes in raid456 stripe cache */
        if (conf->min_nr_stripes != nr_stripes) {
                r = raid5_set_cache_size(mddev, nr_stripes);
                if (r) {
                        rs->ti->error = "Failed to set raid4/5/6 stripe cache size";
                        return r;
                }

                DMINFO("%u stripe cache entries", nr_stripes);
        }

        return 0;
}

/* Return # of data stripes as kept in mddev as of @rs (i.e. as of superblock) */
static unsigned int mddev_data_stripes(struct raid_set *rs)
{
        return rs->md.raid_disks - rs->raid_type->parity_devs;
}

/* Return # of data stripes of @rs (i.e. as of ctr) */
static unsigned int rs_data_stripes(struct raid_set *rs)
{
        return rs->raid_disks - rs->raid_type->parity_devs;
}

/* Calculate the sectors per device and per array used for @rs */
static int rs_set_dev_and_array_sectors(struct raid_set *rs, bool use_mddev)
{
        int delta_disks;
        unsigned int data_stripes;
        struct mddev *mddev = &rs->md;
        struct md_rdev *rdev;
        sector_t array_sectors = rs->ti->len, dev_sectors = rs->ti->len;

        if (use_mddev) {
                delta_disks = mddev->delta_disks;
                data_stripes = mddev_data_stripes(rs);
        } else {
                delta_disks = rs->delta_disks;
                data_stripes = rs_data_stripes(rs);
        }

        /* Special raid1 case w/o delta_disks support (yet) */
        if (rt_is_raid1(rs->raid_type))
                ;
        else if (rt_is_raid10(rs->raid_type)) {
                if (rs->raid10_copies < 2 ||
                    delta_disks < 0) {
                        rs->ti->error = "Bogus raid10 data copies or delta disks";
                        return -EINVAL;
                }

                dev_sectors *= rs->raid10_copies;
                if (sector_div(dev_sectors, data_stripes))
                        goto bad;

                array_sectors = (data_stripes + delta_disks) * dev_sectors;
                if (sector_div(array_sectors, rs->raid10_copies))
                        goto bad;

        } else if (sector_div(dev_sectors, data_stripes))
                goto bad;

        else
                /* Striped layouts */
                array_sectors = (data_stripes + delta_disks) * dev_sectors;

        rdev_for_each(rdev, mddev)
                rdev->sectors = dev_sectors;

        mddev->array_sectors = array_sectors;
        mddev->dev_sectors = dev_sectors;

        return 0;
bad:
        rs->ti->error = "Target length not divisible by number of data devices";
        return -EINVAL;
}

/* Setup recovery on @rs */
static void __rs_setup_recovery(struct raid_set *rs, sector_t dev_sectors)
{
        /* raid0 does not recover */
        if (rs_is_raid0(rs))
                rs->md.recovery_cp = MaxSector;
        /*
         * A raid6 set has to be recovered either
         * completely or for the grown part to
         * ensure proper parity and Q-Syndrome
         */
        else if (rs_is_raid6(rs))
                rs->md.recovery_cp = dev_sectors;
        /*
         * Other raid set types may skip recovery
         * depending on the 'nosync' flag.
         */
        else
                rs->md.recovery_cp = test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags)
                                     ? MaxSector : dev_sectors;
}

/* Setup recovery on @rs based on raid type, device size and 'nosync' flag */
static void rs_setup_recovery(struct raid_set *rs, sector_t dev_sectors)
{
        if (!dev_sectors)
                /* New raid set or 'sync' flag provided */
                __rs_setup_recovery(rs, 0);
        else if (dev_sectors == MaxSector)
                /* Prevent recovery */
                __rs_setup_recovery(rs, MaxSector);
        else if (rs->dev[0].rdev.sectors < dev_sectors)
                /* Grown raid set */
                __rs_setup_recovery(rs, rs->dev[0].rdev.sectors);
        else
                __rs_setup_recovery(rs, MaxSector);
}

static void do_table_event(struct work_struct *ws)
{
        struct raid_set *rs = container_of(ws, struct raid_set, md.event_work);

        smp_rmb(); /* Make sure we access most actual mddev properties */
        if (!rs_is_reshaping(rs))
                rs_set_capacity(rs);
        dm_table_event(rs->ti->table);
}

static int raid_is_congested(struct dm_target_callbacks *cb, int bits)
{
        struct raid_set *rs = container_of(cb, struct raid_set, callbacks);

        return mddev_congested(&rs->md, bits);
}

/*
 * Make sure a valid takover (level switch) is being requested on @rs
 *
 * Conversions of raid sets from one MD personality to another
 * have to conform to restrictions which are enforced here.
 */
static int rs_check_takeover(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;
        unsigned int near_copies;

        if (rs->md.degraded) {
                rs->ti->error = "Can't takeover degraded raid set";
                return -EPERM;
        }

        if (rs_is_reshaping(rs)) {
                rs->ti->error = "Can't takeover reshaping raid set";
                return -EPERM;
        }

        switch (mddev->level) {
        case 0:
                /* raid0 -> raid1/5 with one disk */
                if ((mddev->new_level == 1 || mddev->new_level == 5) &&
                    mddev->raid_disks == 1)
                        return 0;

                /* raid0 -> raid10 */
                if (mddev->new_level == 10 &&
                    !(rs->raid_disks % mddev->raid_disks))
                        return 0;

                /* raid0 with multiple disks -> raid4/5/6 */
                if (__within_range(mddev->new_level, 4, 6) &&
                    mddev->new_layout == ALGORITHM_PARITY_N &&
                    mddev->raid_disks > 1)
                        return 0;

                break;

        case 10:
                /* Can't takeover raid10_offset! */
                if (__is_raid10_offset(mddev->layout))
                        break;

                near_copies = __raid10_near_copies(mddev->layout);

                /* raid10* -> raid0 */
                if (mddev->new_level == 0) {
                        /* Can takeover raid10_near with raid disks divisable by data copies! */
                        if (near_copies > 1 &&
                            !(mddev->raid_disks % near_copies)) {
                                mddev->raid_disks /= near_copies;
                                mddev->delta_disks = mddev->raid_disks;
                                return 0;
                        }

                        /* Can takeover raid10_far */
                        if (near_copies == 1 &&
                            __raid10_far_copies(mddev->layout) > 1)
                                return 0;

                        break;
                }

                /* raid10_{near,far} -> raid1 */
                if (mddev->new_level == 1 &&
                    max(near_copies, __raid10_far_copies(mddev->layout)) == mddev->raid_disks)
                        return 0;

                /* raid10_{near,far} with 2 disks -> raid4/5 */
                if (__within_range(mddev->new_level, 4, 5) &&
                    mddev->raid_disks == 2)
                        return 0;
                break;

        case 1:
                /* raid1 with 2 disks -> raid4/5 */
                if (__within_range(mddev->new_level, 4, 5) &&
                    mddev->raid_disks == 2) {
                        mddev->degraded = 1;
                        return 0;
                }

                /* raid1 -> raid0 */
                if (mddev->new_level == 0 &&
                    mddev->raid_disks == 1)
                        return 0;

                /* raid1 -> raid10 */
                if (mddev->new_level == 10)
                        return 0;
                break;

        case 4:
                /* raid4 -> raid0 */
                if (mddev->new_level == 0)
                        return 0;

                /* raid4 -> raid1/5 with 2 disks */
                if ((mddev->new_level == 1 || mddev->new_level == 5) &&
                    mddev->raid_disks == 2)
                        return 0;

                /* raid4 -> raid5/6 with parity N */
                if (__within_range(mddev->new_level, 5, 6) &&
                    mddev->layout == ALGORITHM_PARITY_N)
                        return 0;
                break;

        case 5:
                /* raid5 with parity N -> raid0 */
                if (mddev->new_level == 0 &&
                    mddev->layout == ALGORITHM_PARITY_N)
                        return 0;

                /* raid5 with parity N -> raid4 */
                if (mddev->new_level == 4 &&
                    mddev->layout == ALGORITHM_PARITY_N)
                        return 0;

                /* raid5 with 2 disks -> raid1/4/10 */
                if ((mddev->new_level == 1 || mddev->new_level == 4 || mddev->new_level == 10) &&
                    mddev->raid_disks == 2)
                        return 0;

                /* raid5_* ->  raid6_*_6 with Q-Syndrome N (e.g. raid5_ra -> raid6_ra_6 */
                if (mddev->new_level == 6 &&
                    ((mddev->layout == ALGORITHM_PARITY_N && mddev->new_layout == ALGORITHM_PARITY_N) ||
                      __within_range(mddev->new_layout, ALGORITHM_LEFT_ASYMMETRIC_6, ALGORITHM_RIGHT_SYMMETRIC_6)))
                        return 0;
                break;

        case 6:
                /* raid6 with parity N -> raid0 */
                if (mddev->new_level == 0 &&
                    mddev->layout == ALGORITHM_PARITY_N)
                        return 0;

                /* raid6 with parity N -> raid4 */
                if (mddev->new_level == 4 &&
                    mddev->layout == ALGORITHM_PARITY_N)
                        return 0;

                /* raid6_*_n with Q-Syndrome N -> raid5_* */
                if (mddev->new_level == 5 &&
                    ((mddev->layout == ALGORITHM_PARITY_N && mddev->new_layout == ALGORITHM_PARITY_N) ||
                     __within_range(mddev->new_layout, ALGORITHM_LEFT_ASYMMETRIC, ALGORITHM_RIGHT_SYMMETRIC)))
                        return 0;

        default:
                break;
        }

        rs->ti->error = "takeover not possible";
        return -EINVAL;
}

/* True if @rs requested to be taken over */
static bool rs_takeover_requested(struct raid_set *rs)
{
        return rs->md.new_level != rs->md.level;
}

/* True if @rs is requested to reshape by ctr */
static bool rs_reshape_requested(struct raid_set *rs)
{
        bool change;
        struct mddev *mddev = &rs->md;

        if (rs_takeover_requested(rs))
                return false;

        if (!mddev->level)
                return false;

        change = mddev->new_layout != mddev->layout ||
                 mddev->new_chunk_sectors != mddev->chunk_sectors ||
                 rs->delta_disks;

        /* Historical case to support raid1 reshape without delta disks */
        if (mddev->level == 1) {
                if (rs->delta_disks)
                        return !!rs->delta_disks;

                return !change &&
                       mddev->raid_disks != rs->raid_disks;
        }

        if (mddev->level == 10)
                return change &&
                       !__is_raid10_far(mddev->new_layout) &&
                       rs->delta_disks >= 0;

        return change;
}

/*  Features */
#define FEATURE_FLAG_SUPPORTS_V190      0x1 /* Supports extended superblock */

/* State flags for sb->flags */
#define SB_FLAG_RESHAPE_ACTIVE          0x1
#define SB_FLAG_RESHAPE_BACKWARDS       0x2

/*
 * This structure is never routinely used by userspace, unlike md superblocks.
 * Devices with this superblock should only ever be accessed via device-mapper.
 */
#define DM_RAID_MAGIC 0x64526D44
struct dm_raid_superblock {
        __le32 magic;           /* "DmRd" */
        __le32 compat_features; /* Used to indicate compatible features (like 1.9.0 ondisk metadata extension) */

        __le32 num_devices;     /* Number of devices in this raid set. (Max 64) */
        __le32 array_position;  /* The position of this drive in the raid set */

        __le64 events;          /* Incremented by md when superblock updated */
        __le64 failed_devices;  /* Pre 1.9.0 part of bit field of devices to */
                                /* indicate failures (see extension below) */

        /*
         * This offset tracks the progress of the repair or replacement of
         * an individual drive.
         */
        __le64 disk_recovery_offset;

        /*
         * This offset tracks the progress of the initial raid set
         * synchronisation/parity calculation.
         */
        __le64 array_resync_offset;

        /*
         * raid characteristics
         */
        __le32 level;
        __le32 layout;
        __le32 stripe_sectors;

        /********************************************************************
         * BELOW FOLLOW V1.9.0 EXTENSIONS TO THE PRISTINE SUPERBLOCK FORMAT!!!
         *
         * FEATURE_FLAG_SUPPORTS_V190 in the features member indicates that those exist
         */

        __le32 flags; /* Flags defining array states for reshaping */

        /*
         * This offset tracks the progress of a raid
         * set reshape in order to be able to restart it
         */
        __le64 reshape_position;

        /*
         * These define the properties of the array in case of an interrupted reshape
         */
        __le32 new_level;
        __le32 new_layout;
        __le32 new_stripe_sectors;
        __le32 delta_disks;

        __le64 array_sectors; /* Array size in sectors */

        /*
         * Sector offsets to data on devices (reshaping).
         * Needed to support out of place reshaping, thus
         * not writing over any stripes whilst converting
         * them from old to new layout
         */
        __le64 data_offset;
        __le64 new_data_offset;

        __le64 sectors; /* Used device size in sectors */

        /*
         * Additonal Bit field of devices indicating failures to support
         * up to 256 devices with the 1.9.0 on-disk metadata format
         */
        __le64 extended_failed_devices[DISKS_ARRAY_ELEMS - 1];

        __le32 incompat_features;       /* Used to indicate any incompatible features */

        /* Always set rest up to logical block size to 0 when writing (see get_metadata_device() below). */
} __packed;

/*
 * Check for reshape constraints on raid set @rs:
 *
 * - reshape function non-existent
 * - degraded set
 * - ongoing recovery
 * - ongoing reshape
 *
 * Returns 0 if none or -EPERM if given constraint
 * and error message reference in @errmsg
 */
static int rs_check_reshape(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;

        if (!mddev->pers || !mddev->pers->check_reshape)
                rs->ti->error = "Reshape not supported";
        else if (mddev->degraded)
                rs->ti->error = "Can't reshape degraded raid set";
        else if (rs_is_recovering(rs))
                rs->ti->error = "Convert request on recovering raid set prohibited";
        else if (rs_is_reshaping(rs))
                rs->ti->error = "raid set already reshaping!";
        else if (!(rs_is_raid1(rs) || rs_is_raid10(rs) || rs_is_raid456(rs)))
                rs->ti->error = "Reshaping only supported for raid1/4/5/6/10";
        else
                return 0;

        return -EPERM;
}

static int read_disk_sb(struct md_rdev *rdev, int size)
{
        BUG_ON(!rdev->sb_page);

        if (rdev->sb_loaded)
                return 0;

        if (!sync_page_io(rdev, 0, size, rdev->sb_page, REQ_OP_READ, 0, true)) {
                DMERR("Failed to read superblock of device at position %d",
                      rdev->raid_disk);
                md_error(rdev->mddev, rdev);
                return -EINVAL;
        }

        rdev->sb_loaded = 1;

        return 0;
}

static void sb_retrieve_failed_devices(struct dm_raid_superblock *sb, uint64_t *failed_devices)
{
        failed_devices[0] = le64_to_cpu(sb->failed_devices);
        memset(failed_devices + 1, 0, sizeof(sb->extended_failed_devices));

        if (le32_to_cpu(sb->compat_features) & FEATURE_FLAG_SUPPORTS_V190) {
                int i = ARRAY_SIZE(sb->extended_failed_devices);

                while (i--)
                        failed_devices[i+1] = le64_to_cpu(sb->extended_failed_devices[i]);
        }
}

static void sb_update_failed_devices(struct dm_raid_superblock *sb, uint64_t *failed_devices)
{
        int i = ARRAY_SIZE(sb->extended_failed_devices);

        sb->failed_devices = cpu_to_le64(failed_devices[0]);
        while (i--)
                sb->extended_failed_devices[i] = cpu_to_le64(failed_devices[i+1]);
}

/*
 * Synchronize the superblock members with the raid set properties
 *
 * All superblock data is little endian.
 */
static void super_sync(struct mddev *mddev, struct md_rdev *rdev)
{
        bool update_failed_devices = false;
        unsigned int i;
        uint64_t failed_devices[DISKS_ARRAY_ELEMS];
        struct dm_raid_superblock *sb;
        struct raid_set *rs = container_of(mddev, struct raid_set, md);

        /* No metadata device, no superblock */
        if (!rdev->meta_bdev)
                return;

        BUG_ON(!rdev->sb_page);

        sb = page_address(rdev->sb_page);

        sb_retrieve_failed_devices(sb, failed_devices);

        for (i = 0; i < rs->raid_disks; i++)
                if (!rs->dev[i].data_dev || test_bit(Faulty, &rs->dev[i].rdev.flags)) {
                        update_failed_devices = true;
                        set_bit(i, (void *) failed_devices);
                }

        if (update_failed_devices)
                sb_update_failed_devices(sb, failed_devices);

        sb->magic = cpu_to_le32(DM_RAID_MAGIC);
        sb->compat_features = cpu_to_le32(FEATURE_FLAG_SUPPORTS_V190);

        sb->num_devices = cpu_to_le32(mddev->raid_disks);
        sb->array_position = cpu_to_le32(rdev->raid_disk);

        sb->events = cpu_to_le64(mddev->events);

        sb->disk_recovery_offset = cpu_to_le64(rdev->recovery_offset);
        sb->array_resync_offset = cpu_to_le64(mddev->recovery_cp);

        sb->level = cpu_to_le32(mddev->level);
        sb->layout = cpu_to_le32(mddev->layout);
        sb->stripe_sectors = cpu_to_le32(mddev->chunk_sectors);

        sb->new_level = cpu_to_le32(mddev->new_level);
        sb->new_layout = cpu_to_le32(mddev->new_layout);
        sb->new_stripe_sectors = cpu_to_le32(mddev->new_chunk_sectors);

        sb->delta_disks = cpu_to_le32(mddev->delta_disks);

        smp_rmb(); /* Make sure we access most recent reshape position */
        sb->reshape_position = cpu_to_le64(mddev->reshape_position);
        if (le64_to_cpu(sb->reshape_position) != MaxSector) {
                /* Flag ongoing reshape */
                sb->flags |= cpu_to_le32(SB_FLAG_RESHAPE_ACTIVE);

                if (mddev->delta_disks < 0 || mddev->reshape_backwards)
                        sb->flags |= cpu_to_le32(SB_FLAG_RESHAPE_BACKWARDS);
        } else {
                /* Clear reshape flags */
                sb->flags &= ~(cpu_to_le32(SB_FLAG_RESHAPE_ACTIVE|SB_FLAG_RESHAPE_BACKWARDS));
        }

        sb->array_sectors = cpu_to_le64(mddev->array_sectors);
        sb->data_offset = cpu_to_le64(rdev->data_offset);
        sb->new_data_offset = cpu_to_le64(rdev->new_data_offset);
        sb->sectors = cpu_to_le64(rdev->sectors);
        sb->incompat_features = cpu_to_le32(0);

        /* Zero out the rest of the payload after the size of the superblock */
        memset(sb + 1, 0, rdev->sb_size - sizeof(*sb));
}

/*
 * super_load
 *
 * This function creates a superblock if one is not found on the device
 * and will decide which superblock to use if there's a choice.
 *
 * Return: 1 if use rdev, 0 if use refdev, -Exxx otherwise
 */
static int super_load(struct md_rdev *rdev, struct md_rdev *refdev)
{
        int r;
        struct dm_raid_superblock *sb;
        struct dm_raid_superblock *refsb;
        uint64_t events_sb, events_refsb;

        rdev->sb_start = 0;
        rdev->sb_size = bdev_logical_block_size(rdev->meta_bdev);
        if (rdev->sb_size < sizeof(*sb) || rdev->sb_size > PAGE_SIZE) {
                DMERR("superblock size of a logical block is no longer valid");
                return -EINVAL;
        }

        r = read_disk_sb(rdev, rdev->sb_size);
        if (r)
                return r;

        sb = page_address(rdev->sb_page);

        /*
         * Two cases that we want to write new superblocks and rebuild:
         * 1) New device (no matching magic number)
         * 2) Device specified for rebuild (!In_sync w/ offset == 0)
         */
        if ((sb->magic != cpu_to_le32(DM_RAID_MAGIC)) ||
            (!test_bit(In_sync, &rdev->flags) && !rdev->recovery_offset)) {
                super_sync(rdev->mddev, rdev);

                set_bit(FirstUse, &rdev->flags);
                sb->compat_features = cpu_to_le32(FEATURE_FLAG_SUPPORTS_V190);

                /* Force writing of superblocks to disk */
                set_bit(MD_CHANGE_DEVS, &rdev->mddev->flags);

                /* Any superblock is better than none, choose that if given */
                return refdev ? 0 : 1;
        }

        if (!refdev)
                return 1;

        events_sb = le64_to_cpu(sb->events);

        refsb = page_address(refdev->sb_page);
        events_refsb = le64_to_cpu(refsb->events);

        return (events_sb > events_refsb) ? 1 : 0;
}

static int super_init_validation(struct raid_set *rs, struct md_rdev *rdev)
{
        int role;
        unsigned int d;
        struct mddev *mddev = &rs->md;
        uint64_t events_sb;
        uint64_t failed_devices[DISKS_ARRAY_ELEMS];
        struct dm_raid_superblock *sb;
        uint32_t new_devs = 0, rebuild_and_new = 0, rebuilds = 0;
        struct md_rdev *r;
        struct dm_raid_superblock *sb2;

        sb = page_address(rdev->sb_page);
        events_sb = le64_to_cpu(sb->events);

        /*
         * Initialise to 1 if this is a new superblock.
         */
        mddev->events = events_sb ? : 1;

        mddev->reshape_position = MaxSector;

        /*
         * Reshaping is supported, e.g. reshape_position is valid
         * in superblock and superblock content is authoritative.
         */
        if (le32_to_cpu(sb->compat_features) & FEATURE_FLAG_SUPPORTS_V190) {
                /* Superblock is authoritative wrt given raid set layout! */
                mddev->raid_disks = le32_to_cpu(sb->num_devices);
                mddev->level = le32_to_cpu(sb->level);
                mddev->layout = le32_to_cpu(sb->layout);
                mddev->chunk_sectors = le32_to_cpu(sb->stripe_sectors);
                mddev->new_level = le32_to_cpu(sb->new_level);
                mddev->new_layout = le32_to_cpu(sb->new_layout);
                mddev->new_chunk_sectors = le32_to_cpu(sb->new_stripe_sectors);
                mddev->delta_disks = le32_to_cpu(sb->delta_disks);
                mddev->array_sectors = le64_to_cpu(sb->array_sectors);

                /* raid was reshaping and got interrupted */
                if (le32_to_cpu(sb->flags) & SB_FLAG_RESHAPE_ACTIVE) {
                        if (test_bit(__CTR_FLAG_DELTA_DISKS, &rs->ctr_flags)) {
                                DMERR("Reshape requested but raid set is still reshaping");
                                return -EINVAL;
                        }

                        if (mddev->delta_disks < 0 ||
                            (!mddev->delta_disks && (le32_to_cpu(sb->flags) & SB_FLAG_RESHAPE_BACKWARDS)))
                                mddev->reshape_backwards = 1;
                        else
                                mddev->reshape_backwards = 0;

                        mddev->reshape_position = le64_to_cpu(sb->reshape_position);
                        rs->raid_type = get_raid_type_by_ll(mddev->level, mddev->layout);
                }

        } else {
                /*
                 * No takeover/reshaping, because we don't have the extended v1.9.0 metadata
                 */
                if (le32_to_cpu(sb->level) != mddev->level) {
                        DMERR("Reshaping/takeover raid sets not yet supported. (raid level/stripes/size change)");
                        return -EINVAL;
                }
                if (le32_to_cpu(sb->layout) != mddev->layout) {
                        DMERR("Reshaping raid sets not yet supported. (raid layout change)");
                        DMERR("  0x%X vs 0x%X", le32_to_cpu(sb->layout), mddev->layout);
                        DMERR("  Old layout: %s w/ %d copies",
                              raid10_md_layout_to_format(le32_to_cpu(sb->layout)),
                              raid10_md_layout_to_copies(le32_to_cpu(sb->layout)));
                        DMERR("  New layout: %s w/ %d copies",
                              raid10_md_layout_to_format(mddev->layout),
                              raid10_md_layout_to_copies(mddev->layout));
                        return -EINVAL;
                }
                if (le32_to_cpu(sb->stripe_sectors) != mddev->chunk_sectors) {
                        DMERR("Reshaping raid sets not yet supported. (stripe sectors change)");
                        return -EINVAL;
                }

                /* We can only change the number of devices in raid1 with old (i.e. pre 1.0.7) metadata */
                if (!rt_is_raid1(rs->raid_type) &&
                    (le32_to_cpu(sb->num_devices) != mddev->raid_disks)) {
                        DMERR("Reshaping raid sets not yet supported. (device count change from %u to %u)",
                              sb->num_devices, mddev->raid_disks);
                        return -EINVAL;
                }

                /* Table line is checked vs. authoritative superblock */
                rs_set_new(rs);
        }

        if (!test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags))
                mddev->recovery_cp = le64_to_cpu(sb->array_resync_offset);

        /*
         * During load, we set FirstUse if a new superblock was written.
         * There are two reasons we might not have a superblock:
         * 1) The raid set is brand new - in which case, all of the
         *    devices must have their In_sync bit set.  Also,
         *    recovery_cp must be 0, unless forced.
         * 2) This is a new device being added to an old raid set
         *    and the new device needs to be rebuilt - in which
         *    case the In_sync bit will /not/ be set and
         *    recovery_cp must be MaxSector.
         * 3) This is/are a new device(s) being added to an old
         *    raid set during takeover to a higher raid level
         *    to provide capacity for redundancy or during reshape
         *    to add capacity to grow the raid set.
         */
        d = 0;
        rdev_for_each(r, mddev) {
                if (test_bit(FirstUse, &r->flags))
                        new_devs++;

                if (!test_bit(In_sync, &r->flags)) {
                        DMINFO("Device %d specified for rebuild; clearing superblock",
                                r->raid_disk);
                        rebuilds++;

                        if (test_bit(FirstUse, &r->flags))
                                rebuild_and_new++;
                }

                d++;
        }

        if (new_devs == rs->raid_disks || !rebuilds) {
                /* Replace a broken device */
                if (new_devs == 1 && !rs->delta_disks)
                        ;
                if (new_devs == rs->raid_disks) {
                        DMINFO("Superblocks created for new raid set");
                        set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
                } else if (new_devs != rebuilds &&
                           new_devs != rs->delta_disks) {
                        DMERR("New device injected into existing raid set without "
                              "'delta_disks' or 'rebuild' parameter specified");
                        return -EINVAL;
                }
        } else if (new_devs && new_devs != rebuilds) {
                DMERR("%u 'rebuild' devices cannot be injected into"
                      " a raid set with %u other first-time devices",
                      rebuilds, new_devs);
                return -EINVAL;
        } else if (rebuilds) {
                if (rebuild_and_new && rebuilds != rebuild_and_new) {
                        DMERR("new device%s provided without 'rebuild'",
                              new_devs > 1 ? "s" : "");
                        return -EINVAL;
                } else if (rs_is_recovering(rs)) {
                        DMERR("'rebuild' specified while raid set is not in-sync (recovery_cp=%llu)",
                              (unsigned long long) mddev->recovery_cp);
                        return -EINVAL;
                } else if (rs_is_reshaping(rs)) {
                        DMERR("'rebuild' specified while raid set is being reshaped (reshape_position=%llu)",
                              (unsigned long long) mddev->reshape_position);
                        return -EINVAL;
                }
        }

        /*
         * Now we set the Faulty bit for those devices that are
         * recorded in the superblock as failed.
         */
        sb_retrieve_failed_devices(sb, failed_devices);
        rdev_for_each(r, mddev) {
                if (!r->sb_page)
                        continue;
                sb2 = page_address(r->sb_page);
                sb2->failed_devices = 0;
                memset(sb2->extended_failed_devices, 0, sizeof(sb2->extended_failed_devices));

                /*
                 * Check for any device re-ordering.
                 */
                if (!test_bit(FirstUse, &r->flags) && (r->raid_disk >= 0)) {
                        role = le32_to_cpu(sb2->array_position);
                        if (role < 0)
                                continue;

                        if (role != r->raid_disk) {
                                if (__is_raid10_near(mddev->layout)) {
                                        if (mddev->raid_disks % __raid10_near_copies(mddev->layout) ||
                                            rs->raid_disks % rs->raid10_copies) {
                                                rs->ti->error =
                                                        "Cannot change raid10 near set to odd # of devices!";
                                                return -EINVAL;
                                        }

                                        sb2->array_position = cpu_to_le32(r->raid_disk);

                                } else if (!(rs_is_raid10(rs) && rt_is_raid0(rs->raid_type)) &&
                                           !(rs_is_raid0(rs) && rt_is_raid10(rs->raid_type)) &&
                                           !rt_is_raid1(rs->raid_type)) {
                                        rs->ti->error = "Cannot change device positions in raid set";
                                        return -EINVAL;
                                }

                                DMINFO("raid device #%d now at position #%d", role, r->raid_disk);
                        }

                        /*
                         * Partial recovery is performed on
                         * returning failed devices.
                         */
                        if (test_bit(role, (void *) failed_devices))
                                set_bit(Faulty, &r->flags);
                }
        }

        return 0;
}

static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
{
        struct mddev *mddev = &rs->md;
        struct dm_raid_superblock *sb;

        if (rs_is_raid0(rs) || !rdev->sb_page)
                return 0;

        sb = page_address(rdev->sb_page);

        /*
         * If mddev->events is not set, we know we have not yet initialized
         * the array.
         */
        if (!mddev->events && super_init_validation(rs, rdev))
                return -EINVAL;

        if (le32_to_cpu(sb->compat_features) != FEATURE_FLAG_SUPPORTS_V190) {
                rs->ti->error = "Unable to assemble array: Unknown flag(s) in compatible feature flags";
                return -EINVAL;
        }

        if (sb->incompat_features) {
                rs->ti->error = "Unable to assemble array: No incompatible feature flags supported yet";
                return -EINVAL;
        }

        /* Enable bitmap creation for RAID levels != 0 */
        mddev->bitmap_info.offset = rt_is_raid0(rs->raid_type) ? 0 : to_sector(4096);
        rdev->mddev->bitmap_info.default_offset = mddev->bitmap_info.offset;

        if (!test_and_clear_bit(FirstUse, &rdev->flags)) {
                /* Retrieve device size stored in superblock to be prepared for shrink */
                rdev->sectors = le64_to_cpu(sb->sectors);
                rdev->recovery_offset = le64_to_cpu(sb->disk_recovery_offset);
                if (rdev->recovery_offset == MaxSector)
                        set_bit(In_sync, &rdev->flags);
                /*
                 * If no reshape in progress -> we're recovering single
                 * disk(s) and have to set the device(s) to out-of-sync
                 */
                else if (!rs_is_reshaping(rs))
                        clear_bit(In_sync, &rdev->flags); /* Mandatory for recovery */
        }

        /*
         * If a device comes back, set it as not In_sync and no longer faulty.
         */
        if (test_and_clear_bit(Faulty, &rdev->flags)) {
                rdev->recovery_offset = 0;
                clear_bit(In_sync, &rdev->flags);
                rdev->saved_raid_disk = rdev->raid_disk;
        }

        /* Reshape support -> restore repective data offsets */
        rdev->data_offset = le64_to_cpu(sb->data_offset);
        rdev->new_data_offset = le64_to_cpu(sb->new_data_offset);

        return 0;
}

/*
 * Analyse superblocks and select the freshest.
 */
static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
{
        int r;
        struct raid_dev *dev;
        struct md_rdev *rdev, *tmp, *freshest;
        struct mddev *mddev = &rs->md;

        freshest = NULL;
        rdev_for_each_safe(rdev, tmp, mddev) {
                /*
                 * Skipping super_load due to CTR_FLAG_SYNC will cause
                 * the array to undergo initialization again as
                 * though it were new.  This is the intended effect
                 * of the "sync" directive.
                 *
                 * When reshaping capability is added, we must ensure
                 * that the "sync" directive is disallowed during the
                 * reshape.
                 */
                if (test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags))
                        continue;

                if (!rdev->meta_bdev)
                        continue;

                r = super_load(rdev, freshest);

                switch (r) {
                case 1:
                        freshest = rdev;
                        break;
                case 0:
                        break;
                default:
                        dev = container_of(rdev, struct raid_dev, rdev);
                        if (dev->meta_dev)
                                dm_put_device(ti, dev->meta_dev);

                        dev->meta_dev = NULL;
                        rdev->meta_bdev = NULL;

                        if (rdev->sb_page)
                                put_page(rdev->sb_page);

                        rdev->sb_page = NULL;

                        rdev->sb_loaded = 0;

                        /*
                         * We might be able to salvage the data device
                         * even though the meta device has failed.  For
                         * now, we behave as though '- -' had been
                         * set for this device in the table.
                         */
                        if (dev->data_dev)
                                dm_put_device(ti, dev->data_dev);

                        dev->data_dev = NULL;
                        rdev->bdev = NULL;

                        list_del(&rdev->same_set);
                }
        }

        if (!freshest)
                return 0;

        if (validate_raid_redundancy(rs)) {
                rs->ti->error = "Insufficient redundancy to activate array";
                return -EINVAL;
        }

        /*
         * Validation of the freshest device provides the source of
         * validation for the remaining devices.
         */
        rs->ti->error = "Unable to assemble array: Invalid superblocks";
        if (super_validate(rs, freshest))
                return -EINVAL;

        rdev_for_each(rdev, mddev)
                if ((rdev != freshest) && super_validate(rs, rdev))
                        return -EINVAL;
        return 0;
}

/*
 * Adjust data_offset and new_data_offset on all disk members of @rs
 * for out of place reshaping if requested by contructor
 *
 * We need free space at the beginning of each raid disk for forward
 * and at the end for backward reshapes which userspace has to provide
 * via remapping/reordering of space.
 */
static int rs_adjust_data_offsets(struct raid_set *rs)
{
        sector_t data_offset = 0, new_data_offset = 0;
        struct md_rdev *rdev;

        /* Constructor did not request data offset change */
        if (!test_bit(__CTR_FLAG_DATA_OFFSET, &rs->ctr_flags)) {
                if (!rs_is_reshapable(rs))
                        goto out;

                return 0;
        }

        /* HM FIXME: get InSync raid_dev? */
        rdev = &rs->dev[0].rdev;

        if (rs->delta_disks < 0) {
                /*
                 * Removing disks (reshaping backwards):
                 *
                 * - before reshape: data is at offset 0 and free space
                 *                   is at end of each component LV
                 *
                 * - after reshape: data is at offset rs->data_offset != 0 on each component LV
                 */
                data_offset = 0;
                new_data_offset = rs->data_offset;

        } else if (rs->delta_disks > 0) {
                /*
                 * Adding disks (reshaping forwards):
                 *
                 * - before reshape: data is at offset rs->data_offset != 0 and
                 *                   free space is at begin of each component LV
                 *
                 * - after reshape: data is at offset 0 on each component LV
                 */
                data_offset = rs->data_offset;
                new_data_offset = 0;

        } else {
                /*
                 * User space passes in 0 for data offset after having removed reshape space
                 *
                 * - or - (data offset != 0)
                 *
                 * Changing RAID layout or chunk size -> toggle offsets
                 *
                 * - before reshape: data is at offset rs->data_offset 0 and
                 *                   free space is at end of each component LV
                 *                   -or-
                 *                   data is at offset rs->data_offset != 0 and
                 *                   free space is at begin of each component LV
                 *
                 * - after reshape: data is at offset 0 if it was at offset != 0
                 *                  or at offset != 0 if it was at offset 0
                 *                  on each component LV
                 *
                 */
                data_offset = rs->data_offset ? rdev->data_offset : 0;
                new_data_offset = data_offset ? 0 : rs->data_offset;
                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
        }

        /*
         * Make sure we got a minimum amount of free sectors per device
         */
        if (rs->data_offset &&
            to_sector(i_size_read(rdev->bdev->bd_inode)) - rdev->sectors < MIN_FREE_RESHAPE_SPACE) {
                rs->ti->error = data_offset ? "No space for forward reshape" :
                                              "No space for backward reshape";
                return -ENOSPC;
        }
out:
        /* Adjust data offsets on all rdevs */
        rdev_for_each(rdev, &rs->md) {
                rdev->data_offset = data_offset;
                rdev->new_data_offset = new_data_offset;
        }

        return 0;
}

/* Userpace reordered disks -> adjust raid_disk indexes in @rs */
static void __reorder_raid_disk_indexes(struct raid_set *rs)
{
        int i = 0;
        struct md_rdev *rdev;

        rdev_for_each(rdev, &rs->md) {
                rdev->raid_disk = i++;
                rdev->saved_raid_disk = rdev->new_raid_disk = -1;
        }
}

/*
 * Setup @rs for takeover by a different raid level
 */
static int rs_setup_takeover(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;
        struct md_rdev *rdev;
        unsigned int d = mddev->raid_disks = rs->raid_disks;
        sector_t new_data_offset = rs->dev[0].rdev.data_offset ? 0 : rs->data_offset;

        if (rt_is_raid10(rs->raid_type)) {
                if (mddev->level == 0) {
                        /* Userpace reordered disks -> adjust raid_disk indexes */
                        __reorder_raid_disk_indexes(rs);

                        /* raid0 -> raid10_far layout */
                        mddev->layout = raid10_format_to_md_layout(rs, ALGORITHM_RAID10_FAR,
                                                                   rs->raid10_copies);
                } else if (mddev->level == 1)
                        /* raid1 -> raid10_near layout */
                        mddev->layout = raid10_format_to_md_layout(rs, ALGORITHM_RAID10_NEAR,
                                                                   rs->raid_disks);
                else
                        return -EINVAL;

        }

        clear_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
        mddev->recovery_cp = MaxSector;

        while (d--) {
                rdev = &rs->dev[d].rdev;

                if (test_bit(d, (void *) rs->rebuild_disks)) {
                        clear_bit(In_sync, &rdev->flags);
                        clear_bit(Faulty, &rdev->flags);
                        mddev->recovery_cp = rdev->recovery_offset = 0;
                        /* Bitmap has to be created when we do an "up" takeover */
                        set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
                }

                rdev->new_data_offset = new_data_offset;
        }

        return 0;
}

/* Prepare @rs for reshape */
static int rs_prepare_reshape(struct raid_set *rs)
{
        bool reshape;
        struct mddev *mddev = &rs->md;

        if (rs_is_raid10(rs)) {
                if (rs->raid_disks != mddev->raid_disks &&
                    __is_raid10_near(mddev->layout) &&
                    rs->raid10_copies &&
                    rs->raid10_copies != __raid10_near_copies(mddev->layout)) {
                        /*
                         * raid disk have to be multiple of data copies to allow this conversion,
                         *
                         * This is actually not a reshape it is a
                         * rebuild of any additional mirrors per group
                         */
                        if (rs->raid_disks % rs->raid10_copies) {
                                rs->ti->error = "Can't reshape raid10 mirror groups";
                                return -EINVAL;
                        }

                        /* Userpace reordered disks to add/remove mirrors -> adjust raid_disk indexes */
                        __reorder_raid_disk_indexes(rs);
                        mddev->layout = raid10_format_to_md_layout(rs, ALGORITHM_RAID10_NEAR,
                                                                   rs->raid10_copies);
                        mddev->new_layout = mddev->layout;
                        reshape = false;
                } else
                        reshape = true;

        } else if (rs_is_raid456(rs))
                reshape = true;

        else if (rs_is_raid1(rs)) {
                if (rs->delta_disks) {
                        /* Process raid1 via delta_disks */
                        mddev->degraded = rs->delta_disks < 0 ? -rs->delta_disks : rs->delta_disks;
                        reshape = true;
                } else {
                        /* Process raid1 without delta_disks */
                        mddev->raid_disks = rs->raid_disks;
                        reshape = false;
                }
        } else {
                rs->ti->error = "Called with bogus raid type";
                return -EINVAL;
        }

        if (reshape) {
                set_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags);
                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
        } else if (mddev->raid_disks < rs->raid_disks)
                /* Create new superblocks and bitmaps, if any new disks */
                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);

        return 0;
}

/*
 *
 * - change raid layout
 * - change chunk size
 * - add disks
 * - remove disks
 */
static int rs_setup_reshape(struct raid_set *rs)
{
        int r = 0;
        unsigned int cur_raid_devs, d;
        struct mddev *mddev = &rs->md;
        struct md_rdev *rdev;

        mddev->delta_disks = rs->delta_disks;
        cur_raid_devs = mddev->raid_disks;

        /* Ignore impossible layout change whilst adding/removing disks */
        if (mddev->delta_disks &&
            mddev->layout != mddev->new_layout) {
                DMINFO("Ignoring invalid layout change with delta_disks=%d", rs->delta_disks);
                mddev->new_layout = mddev->layout;
        }

        /*
         * Adjust array size:
         *
         * - in case of adding disks, array size has
         *   to grow after the disk adding reshape,
         *   which'll hapen in the event handler;
         *   reshape will happen forward, so space has to
         *   be available at the beginning of each disk
         *
         * - in case of removing disks, array size
         *   has to shrink before starting the reshape,
         *   which'll happen here;
         *   reshape will happen backward, so space has to
         *   be available at the end of each disk
         *
         * - data_offset and new_data_offset are
         *   adjusted for aforementioned out of place
         *   reshaping based on userspace passing in
         *   the "data_offset <sectors>" key/value
         *   pair via the constructor
         */

        /* Add disk(s) */
        if (rs->delta_disks > 0) {
                /* Prepare disks for check in raid4/5/6/10 {check|start}_reshape */
                for (d = cur_raid_devs; d < rs->raid_disks; d++) {
                        rdev = &rs->dev[d].rdev;
                        clear_bit(In_sync, &rdev->flags);

                        /*
                         * save_raid_disk needs to be -1, or recovery_offset will be set to 0
                         * by md, which'll store that erroneously in the superblock on reshape
                         */
                        rdev->saved_raid_disk = -1;
                        rdev->raid_disk = d;

                        rdev->sectors = mddev->dev_sectors;
                        rdev->recovery_offset = rs_is_raid1(rs) ? 0 : MaxSector;
                }

                mddev->reshape_backwards = 0; /* adding disks -> forward reshape */

        /* Remove disk(s) */
        } else if (rs->delta_disks < 0) {
                r = rs_set_dev_and_array_sectors(rs, true);
                mddev->reshape_backwards = 1; /* removing disk(s) -> backward reshape */

        /* Change layout and/or chunk size */
        } else {
                /*
                 * Reshape layout (e.g. raid5_ls -> raid5_n) and/or chunk size:
                 *
                 * keeping number of disks and do layout change ->
                 *
                 * toggle reshape_backward depending on data_offset:
                 *
                 * - free space upfront -> reshape forward
                 *
                 * - free space at the end -> reshape backward
                 *
                 *
                 * This utilizes free reshape space avoiding the need
                 * for userspace to move (parts of) LV segments in
                 * case of layout/chunksize change  (for disk
                 * adding/removing reshape space has to be at
                 * the proper address (see above with delta_disks):
                 *
                 * add disk(s)   -> begin
                 * remove disk(s)-> end
                 */
                mddev->reshape_backwards = rs->dev[0].rdev.data_offset ? 0 : 1;
        }

        return r;
}

/*
 * Enable/disable discard support on RAID set depending on
 * RAID level and discard properties of underlying RAID members.
 */
static void configure_discard_support(struct raid_set *rs)
{
        int i;
        bool raid456;
        struct dm_target *ti = rs->ti;

        /* Assume discards not supported until after checks below. */
        ti->discards_supported = false;

        /* RAID level 4,5,6 require discard_zeroes_data for data integrity! */
        raid456 = (rs->md.level == 4 || rs->md.level == 5 || rs->md.level == 6);

        for (i = 0; i < rs->raid_disks; i++) {
                struct request_queue *q;

                if (!rs->dev[i].rdev.bdev)
                        continue;

                q = bdev_get_queue(rs->dev[i].rdev.bdev);
                if (!q || !blk_queue_discard(q))
                        return;

                if (raid456) {
                        if (!q->limits.discard_zeroes_data)
                                return;
                        if (!devices_handle_discard_safely) {
                                DMERR("raid456 discard support disabled due to discard_zeroes_data uncertainty.");
                                DMERR("Set dm-raid.devices_handle_discard_safely=Y to override.");
                                return;
                        }
                }
        }

        /* All RAID members properly support discards */
        ti->discards_supported = true;

        /*
         * RAID1 and RAID10 personalities require bio splitting,
         * RAID0/4/5/6 don't and process large discard bios properly.
         */
        ti->split_discard_bios = !!(rs->md.level == 1 || rs->md.level == 10);
        ti->num_discard_bios = 1;
}

/*
 * Construct a RAID0/1/10/4/5/6 mapping:
 * Args:
 *      <raid_type> <#raid_params> <raid_params>{0,}    \
 *      <#raid_devs> [<meta_dev1> <dev1>]{1,}
 *
 * <raid_params> varies by <raid_type>.  See 'parse_raid_params' for
 * details on possible <raid_params>.
 *
 * Userspace is free to initialize the metadata devices, hence the superblocks to
 * enforce recreation based on the passed in table parameters.
 *
 */
static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
        int r;
        bool resize;
        struct raid_type *rt;
        unsigned int num_raid_params, num_raid_devs;
        sector_t calculated_dev_sectors;
        struct raid_set *rs = NULL;
        const char *arg;
        struct rs_layout rs_layout;
        struct dm_arg_set as = { argc, argv }, as_nrd;
        struct dm_arg _args[] = {
                { 0, as.argc, "Cannot understand number of raid parameters" },
                { 1, 254, "Cannot understand number of raid devices parameters" }
        };

        /* Must have <raid_type> */
        arg = dm_shift_arg(&as);
        if (!arg) {
                ti->error = "No arguments";
                return -EINVAL;
        }

        rt = get_raid_type(arg);
        if (!rt) {
                ti->error = "Unrecognised raid_type";
                return -EINVAL;
        }

        /* Must have <#raid_params> */
        if (dm_read_arg_group(_args, &as, &num_raid_params, &ti->error))
                return -EINVAL;

        /* number of raid device tupples <meta_dev data_dev> */
        as_nrd = as;
        dm_consume_args(&as_nrd, num_raid_params);
        _args[1].max = (as_nrd.argc - 1) / 2;
        if (dm_read_arg(_args + 1, &as_nrd, &num_raid_devs, &ti->error))
                return -EINVAL;

        if (!__within_range(num_raid_devs, 1, MAX_RAID_DEVICES)) {
                ti->error = "Invalid number of supplied raid devices";
                return -EINVAL;
        }

        rs = raid_set_alloc(ti, rt, num_raid_devs);
        if (IS_ERR(rs))
                return PTR_ERR(rs);

        r = parse_raid_params(rs, &as, num_raid_params);
        if (r)
                goto bad;

        r = parse_dev_params(rs, &as);
        if (r)
                goto bad;

        rs->md.sync_super = super_sync;

        /*
         * Calculate ctr requested array and device sizes to allow
         * for superblock analysis needing device sizes defined.
         *
         * Any existing superblock will overwrite the array and device sizes
         */
        r = rs_set_dev_and_array_sectors(rs, false);
        if (r)
                goto bad;

        calculated_dev_sectors = rs->dev[0].rdev.sectors;

        /*
         * Backup any new raid set level, layout, ...
         * requested to be able to compare to superblock
         * members for conversion decisions.
         */
        rs_config_backup(rs, &rs_layout);

        r = analyse_superblocks(ti, rs);
        if (r)
                goto bad;

        resize = calculated_dev_sectors != rs->dev[0].rdev.sectors;

        INIT_WORK(&rs->md.event_work, do_table_event);
        ti->private = rs;
        ti->num_flush_bios = 1;

        /* Restore any requested new layout for conversion decision */
        rs_config_restore(rs, &rs_layout);

        /*
         * Now that we have any superblock metadata available,
         * check for new, recovering, reshaping, to be taken over,
         * to be reshaped or an existing, unchanged raid set to
         * run in sequence.
         */
        if (test_bit(MD_ARRAY_FIRST_USE, &rs->md.flags)) {
                /* A new raid6 set has to be recovered to ensure proper parity and Q-Syndrome */
                if (rs_is_raid6(rs) &&
                    test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags)) {
                        ti->error = "'nosync' not allowed for new raid6 set";
                        r = -EINVAL;
                        goto bad;
                }
                rs_setup_recovery(rs, 0);
                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
                rs_set_new(rs);
        } else if (rs_is_recovering(rs)) {
                /* A recovering raid set may be resized */
                ; /* skip setup rs */
        } else if (rs_is_reshaping(rs)) {
                /* Have to reject size change request during reshape */
                if (resize) {
                        ti->error = "Can't resize a reshaping raid set";
                        r = -EPERM;
                        goto bad;
                }
                /* skip setup rs */
        } else if (rs_takeover_requested(rs)) {
                if (rs_is_reshaping(rs)) {
                        ti->error = "Can't takeover a reshaping raid set";
                        r = -EPERM;
                        goto bad;
                }

                /*
                 * If a takeover is needed, userspace sets any additional
                 * devices to rebuild and we can check for a valid request here.
                 *
                 * If acceptible, set the level to the new requested
                 * one, prohibit requesting recovery, allow the raid
                 * set to run and store superblocks during resume.
                 */
                r = rs_check_takeover(rs);
                if (r)
                        goto bad;

                r = rs_setup_takeover(rs);
                if (r)
                        goto bad;

                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
                /* Takeover ain't recovery, so disable recovery */
                rs_setup_recovery(rs, MaxSector);
                rs_set_new(rs);
        } else if (rs_reshape_requested(rs)) {
                /*
                  * We can only prepare for a reshape here, because the
                  * raid set needs to run to provide the repective reshape
                  * check functions via its MD personality instance.
                  *
                  * So do the reshape check after md_run() succeeded.
                  */
                r = rs_prepare_reshape(rs);
                if (r)
                        return r;

                /* Reshaping ain't recovery, so disable recovery */
                rs_setup_recovery(rs, MaxSector);
                rs_set_cur(rs);
        } else {
                /* May not set recovery when a device rebuild is requested */
                if (test_bit(__CTR_FLAG_REBUILD, &rs->ctr_flags)) {
                        rs_setup_recovery(rs, MaxSector);
                        set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
                } else
                        rs_setup_recovery(rs, test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags) ?
                                              0 : (resize ? calculated_dev_sectors : MaxSector));
                rs_set_cur(rs);
        }

        /* If constructor requested it, change data and new_data offsets */
        r = rs_adjust_data_offsets(rs);
        if (r)
                goto bad;

        /* Start raid set read-only and assumed clean to change in raid_resume() */
        rs->md.ro = 1;
        rs->md.in_sync = 1;
        set_bit(MD_RECOVERY_FROZEN, &rs->md.recovery);

        /* Has to be held on running the array */
        mddev_lock_nointr(&rs->md);
        r = md_run(&rs->md);
        rs->md.in_sync = 0; /* Assume already marked dirty */

        if (r) {
                ti->error = "Failed to run raid array";
                mddev_unlock(&rs->md);
                goto bad;
        }

        rs->callbacks.congested_fn = raid_is_congested;
        dm_table_add_target_callbacks(ti->table, &rs->callbacks);

        mddev_suspend(&rs->md);

        /* Try to adjust the raid4/5/6 stripe cache size to the stripe size */
        if (rs_is_raid456(rs)) {
                r = rs_set_raid456_stripe_cache(rs);
                if (r)
                        goto bad_stripe_cache;
        }

        /* Now do an early reshape check */
        if (test_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags)) {
                r = rs_check_reshape(rs);
                if (r)
                        goto bad_check_reshape;

                /* Restore new, ctr requested layout to perform check */
                rs_config_restore(rs, &rs_layout);

                if (rs->md.pers->start_reshape) {
                        r = rs->md.pers->check_reshape(&rs->md);
                        if (r) {
                                ti->error = "Reshape check failed";
                                goto bad_check_reshape;
                        }
                }
        }

        mddev_unlock(&rs->md);
        return 0;

bad_stripe_cache:
bad_check_reshape:
        md_stop(&rs->md);
bad:
        raid_set_free(rs);

        return r;
}

static void raid_dtr(struct dm_target *ti)
{
        struct raid_set *rs = ti->private;

        list_del_init(&rs->callbacks.list);
        md_stop(&rs->md);
        raid_set_free(rs);
}

static int raid_map(struct dm_target *ti, struct bio *bio)
{
        struct raid_set *rs = ti->private;
        struct mddev *mddev = &rs->md;

        /*
         * If we're reshaping to add disk(s)), ti->len and
         * mddev->array_sectors will differ during the process
         * (ti->len > mddev->array_sectors), so we have to requeue
         * bios with addresses > mddev->array_sectors here or
         * there will occur accesses past EOD of the component
         * data images thus erroring the raid set.
         */
        if (unlikely(bio_end_sector(bio) > mddev->array_sectors))
                return DM_MAPIO_REQUEUE;

        mddev->pers->make_request(mddev, bio);

        return DM_MAPIO_SUBMITTED;
}

/* Return string describing the current sync action of @mddev */
static const char *decipher_sync_action(struct mddev *mddev)
{
        if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
                return "frozen";

        if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
            (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {
                if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
                        return "reshape";

                if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
                        if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
                                return "resync";
                        else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
                                return "check";
                        return "repair";
                }

                if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery))
                        return "recover";
        }

        return "idle";
}

/*
 * Return status string @rdev
 *
 * Status characters:
 *
 *  'D' = Dead/Failed device
 *  'a' = Alive but not in-sync
 *  'A' = Alive and in-sync
 */
static const char *__raid_dev_status(struct md_rdev *rdev, bool array_in_sync)
{
        if (test_bit(Faulty, &rdev->flags))
                return "D";
        else if (!array_in_sync || !test_bit(In_sync, &rdev->flags))
                return "a";
        else
                return "A";
}

/* Helper to return resync/reshape progress for @rs and @array_in_sync */
static sector_t rs_get_progress(struct raid_set *rs,
                                sector_t resync_max_sectors, bool *array_in_sync)
{
        sector_t r, recovery_cp, curr_resync_completed;
        struct mddev *mddev = &rs->md;

        curr_resync_completed = mddev->curr_resync_completed ?: mddev->recovery_cp;
        recovery_cp = mddev->recovery_cp;
        *array_in_sync = false;

        if (rs_is_raid0(rs)) {
                r = resync_max_sectors;
                *array_in_sync = true;

        } else {
                r = mddev->reshape_position;

                /* Reshape is relative to the array size */
                if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) ||
                    r != MaxSector) {
                        if (r == MaxSector) {
                                *array_in_sync = true;
                                r = resync_max_sectors;
                        } else {
                                /* Got to reverse on backward reshape */
                                if (mddev->reshape_backwards)
                                        r = mddev->array_sectors - r;

                                /* Devide by # of data stripes */
                                sector_div(r, mddev_data_stripes(rs));
                        }

                /* Sync is relative to the component device size */
                } else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
                        r = curr_resync_completed;
                else
                        r = recovery_cp;

                if (r == MaxSector) {
                        /*
                         * Sync complete.
                         */
                        *array_in_sync = true;
                        r = resync_max_sectors;
                } else if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
                        /*
                         * If "check" or "repair" is occurring, the raid set has
                         * undergone an initial sync and the health characters
                         * should not be 'a' anymore.
                         */
                        *array_in_sync = true;
                } else {
                        struct md_rdev *rdev;

                        /*
                         * The raid set may be doing an initial sync, or it may
                         * be rebuilding individual components.  If all the
                         * devices are In_sync, then it is the raid set that is
                         * being initialized.
                         */
                        rdev_for_each(rdev, mddev)
                                if (!test_bit(In_sync, &rdev->flags))
                                        *array_in_sync = true;
#if 0
                        r = 0; /* HM FIXME: TESTME: https://bugzilla.redhat.com/show_bug.cgi?id=1210637 ? */
#endif
                }
        }

        return r;
}

/* Helper to return @dev name or "-" if !@dev */
static const char *__get_dev_name(struct dm_dev *dev)
{
        return dev ? dev->name : "-";
}

static void raid_status(struct dm_target *ti, status_type_t type,
                        unsigned int status_flags, char *result, unsigned int maxlen)
{
        struct raid_set *rs = ti->private;
        struct mddev *mddev = &rs->md;
        struct r5conf *conf = mddev->private;
        int i, max_nr_stripes = conf ? conf->max_nr_stripes : 0;
        bool array_in_sync;
        unsigned int raid_param_cnt = 1; /* at least 1 for chunksize */
        unsigned int sz = 0;
        unsigned int rebuild_disks;
        unsigned int write_mostly_params = 0;
        sector_t progress, resync_max_sectors, resync_mismatches;
        const char *sync_action;
        struct raid_type *rt;
        struct md_rdev *rdev;

        switch (type) {
        case STATUSTYPE_INFO:
                /* *Should* always succeed */
                rt = get_raid_type_by_ll(mddev->new_level, mddev->new_layout);
                if (!rt)
                        return;

                DMEMIT("%s %d ", rt->name, mddev->raid_disks);

                /* Access most recent mddev properties for status output */
                smp_rmb();
                /* Get sensible max sectors even if raid set not yet started */
                resync_max_sectors = test_bit(RT_FLAG_RS_PRERESUMED, &rs->runtime_flags) ?
                                      mddev->resync_max_sectors : mddev->dev_sectors;
                progress = rs_get_progress(rs, resync_max_sectors, &array_in_sync);
                resync_mismatches = (mddev->last_sync_action && !strcasecmp(mddev->last_sync_action, "check")) ?
                                    atomic64_read(&mddev->resync_mismatches) : 0;
                sync_action = decipher_sync_action(&rs->md);

                /* HM FIXME: do we want another state char for raid0? It shows 'D' or 'A' now */
                rdev_for_each(rdev, mddev)
                        DMEMIT(__raid_dev_status(rdev, array_in_sync));

                /*
                 * In-sync/Reshape ratio:
                 *  The in-sync ratio shows the progress of:
                 *   - Initializing the raid set
                 *   - Rebuilding a subset of devices of the raid set
                 *  The user can distinguish between the two by referring
                 *  to the status characters.
                 *
                 *  The reshape ratio shows the progress of
                 *  changing the raid layout or the number of
                 *  disks of a raid set
                 */
                DMEMIT(" %llu/%llu", (unsigned long long) progress,
                                     (unsigned long long) resync_max_sectors);

                /*
                 * v1.5.0+:
                 *
                 * Sync action:
                 *   See Documentation/device-mapper/dm-raid.txt for
                 *   information on each of these states.
                 */
                DMEMIT(" %s", sync_action);

                /*
                 * v1.5.0+:
                 *
                 * resync_mismatches/mismatch_cnt
                 *   This field shows the number of discrepancies found when
                 *   performing a "check" of the raid set.
                 */
                DMEMIT(" %llu", (unsigned long long) resync_mismatches);

                /*
                 * v1.9.0+:
                 *
                 * data_offset (needed for out of space reshaping)
                 *   This field shows the data offset into the data
                 *   image LV where the first stripes data starts.
                 *
                 * We keep data_offset equal on all raid disks of the set,
                 * so retrieving it from the first raid disk is sufficient.
                 */
                DMEMIT(" %llu", (unsigned long long) rs->dev[0].rdev.data_offset);
                break;

        case STATUSTYPE_TABLE:
                /* Report the table line string you would use to construct this raid set */

                /* Calculate raid parameter count */
                for (i = 0; i < rs->raid_disks; i++)
                        if (test_bit(WriteMostly, &rs->dev[i].rdev.flags))
                                write_mostly_params += 2;
                rebuild_disks = memweight(rs->rebuild_disks, DISKS_ARRAY_ELEMS * sizeof(*rs->rebuild_disks));
                raid_param_cnt += rebuild_disks * 2 +
                                  write_mostly_params +
                                  hweight32(rs->ctr_flags & CTR_FLAG_OPTIONS_NO_ARGS) +
                                  hweight32(rs->ctr_flags & CTR_FLAG_OPTIONS_ONE_ARG) * 2;
                /* Emit table line */
                DMEMIT("%s %u %u", rs->raid_type->name, raid_param_cnt, mddev->new_chunk_sectors);
                if (test_bit(__CTR_FLAG_RAID10_FORMAT, &rs->ctr_flags))
                        DMEMIT(" %s %s", dm_raid_arg_name_by_flag(CTR_FLAG_RAID10_FORMAT),
                                         raid10_md_layout_to_format(mddev->layout));
                if (test_bit(__CTR_FLAG_RAID10_COPIES, &rs->ctr_flags))
                        DMEMIT(" %s %d", dm_raid_arg_name_by_flag(CTR_FLAG_RAID10_COPIES),
                                         raid10_md_layout_to_copies(mddev->layout));
                if (test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags))
                        DMEMIT(" %s", dm_raid_arg_name_by_flag(CTR_FLAG_NOSYNC));
                if (test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags))
                        DMEMIT(" %s", dm_raid_arg_name_by_flag(CTR_FLAG_SYNC));
                if (test_bit(__CTR_FLAG_REGION_SIZE, &rs->ctr_flags))
                        DMEMIT(" %s %llu", dm_raid_arg_name_by_flag(CTR_FLAG_REGION_SIZE),
                                           (unsigned long long) to_sector(mddev->bitmap_info.chunksize));
                if (test_bit(__CTR_FLAG_DATA_OFFSET, &rs->ctr_flags))
                        DMEMIT(" %s %llu", dm_raid_arg_name_by_flag(CTR_FLAG_DATA_OFFSET),
                                           (unsigned long long) rs->data_offset);
                if (test_bit(__CTR_FLAG_DAEMON_SLEEP, &rs->ctr_flags))
                        DMEMIT(" %s %lu", dm_raid_arg_name_by_flag(CTR_FLAG_DAEMON_SLEEP),
                                          mddev->bitmap_info.daemon_sleep);
                if (test_bit(__CTR_FLAG_DELTA_DISKS, &rs->ctr_flags))
                        DMEMIT(" %s %d", dm_raid_arg_name_by_flag(CTR_FLAG_DELTA_DISKS),
                                         max(rs->delta_disks, mddev->delta_disks));
                if (test_bit(__CTR_FLAG_STRIPE_CACHE, &rs->ctr_flags))
                        DMEMIT(" %s %d", dm_raid_arg_name_by_flag(CTR_FLAG_STRIPE_CACHE),
                                         max_nr_stripes);
                if (rebuild_disks)
                        for (i = 0; i < rs->raid_disks; i++)
                                if (test_bit(rs->dev[i].rdev.raid_disk, (void *) rs->rebuild_disks))
                                        DMEMIT(" %s %u", dm_raid_arg_name_by_flag(CTR_FLAG_REBUILD),
                                                         rs->dev[i].rdev.raid_disk);
                if (write_mostly_params)
                        for (i = 0; i < rs->raid_disks; i++)
                                if (test_bit(WriteMostly, &rs->dev[i].rdev.flags))
                                        DMEMIT(" %s %d", dm_raid_arg_name_by_flag(CTR_FLAG_WRITE_MOSTLY),
                                               rs->dev[i].rdev.raid_disk);
                if (test_bit(__CTR_FLAG_MAX_WRITE_BEHIND, &rs->ctr_flags))
                        DMEMIT(" %s %lu", dm_raid_arg_name_by_flag(CTR_FLAG_MAX_WRITE_BEHIND),
                                          mddev->bitmap_info.max_write_behind);
                if (test_bit(__CTR_FLAG_MAX_RECOVERY_RATE, &rs->ctr_flags))
                        DMEMIT(" %s %d", dm_raid_arg_name_by_flag(CTR_FLAG_MAX_RECOVERY_RATE),
                                         mddev->sync_speed_max);
                if (test_bit(__CTR_FLAG_MIN_RECOVERY_RATE, &rs->ctr_flags))
                        DMEMIT(" %s %d", dm_raid_arg_name_by_flag(CTR_FLAG_MIN_RECOVERY_RATE),
                                         mddev->sync_speed_min);
                DMEMIT(" %d", rs->raid_disks);
                for (i = 0; i < rs->raid_disks; i++)
                        DMEMIT(" %s %s", __get_dev_name(rs->dev[i].meta_dev),
                                         __get_dev_name(rs->dev[i].data_dev));
        }
}

static int raid_message(struct dm_target *ti, unsigned int argc, char **argv)
{
        struct raid_set *rs = ti->private;
        struct mddev *mddev = &rs->md;

        if (!mddev->pers || !mddev->pers->sync_request)
                return -EINVAL;

        if (!strcasecmp(argv[0], "frozen"))
                set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
        else
                clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

        if (!strcasecmp(argv[0], "idle") || !strcasecmp(argv[0], "frozen")) {
                if (mddev->sync_thread) {
                        set_bit(MD_RECOVERY_INTR, &mddev->recovery);
                        md_reap_sync_thread(mddev);
                }
        } else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
                   test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
                return -EBUSY;
        else if (!strcasecmp(argv[0], "resync"))
                ; /* MD_RECOVERY_NEEDED set below */
        else if (!strcasecmp(argv[0], "recover"))
                set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
        else {
                if (!strcasecmp(argv[0], "check"))
                        set_bit(MD_RECOVERY_CHECK, &mddev->recovery);
                else if (!!strcasecmp(argv[0], "repair"))
                        return -EINVAL;
                set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
                set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
        }
        if (mddev->ro == 2) {
                /* A write to sync_action is enough to justify
                 * canceling read-auto mode
                 */
                mddev->ro = 0;
                if (!mddev->suspended && mddev->sync_thread)
                        md_wakeup_thread(mddev->sync_thread);
        }
        set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
        if (!mddev->suspended && mddev->thread)
                md_wakeup_thread(mddev->thread);

        return 0;
}

static int raid_iterate_devices(struct dm_target *ti,
                                iterate_devices_callout_fn fn, void *data)
{
        struct raid_set *rs = ti->private;
        unsigned int i;
        int r = 0;

        for (i = 0; !r && i < rs->md.raid_disks; i++)
                if (rs->dev[i].data_dev)
                        r = fn(ti,
                                 rs->dev[i].data_dev,
                                 0, /* No offset on data devs */
                                 rs->md.dev_sectors,
                                 data);

        return r;
}

static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
        struct raid_set *rs = ti->private;
        unsigned int chunk_size = to_bytes(rs->md.chunk_sectors);

        blk_limits_io_min(limits, chunk_size);
        blk_limits_io_opt(limits, chunk_size * mddev_data_stripes(rs));
}

static void raid_presuspend(struct dm_target *ti)
{
        struct raid_set *rs = ti->private;

        md_stop_writes(&rs->md);
}

static void raid_postsuspend(struct dm_target *ti)
{
        struct raid_set *rs = ti->private;

        if (!rs->md.suspended)
                mddev_suspend(&rs->md);

        rs->md.ro = 1;
}

static void attempt_restore_of_faulty_devices(struct raid_set *rs)
{
        int i;
        uint64_t failed_devices, cleared_failed_devices = 0;
        unsigned long flags;
        struct dm_raid_superblock *sb;
        struct md_rdev *r;

        for (i = 0; i < rs->md.raid_disks; i++) {
                r = &rs->dev[i].rdev;
                if (test_bit(Faulty, &r->flags) && r->sb_page &&
                    sync_page_io(r, 0, r->sb_size, r->sb_page,
                                 REQ_OP_READ, 0, true)) {
                        DMINFO("Faulty %s device #%d has readable super block."
                               "  Attempting to revive it.",
                               rs->raid_type->name, i);

                        /*
                         * Faulty bit may be set, but sometimes the array can
                         * be suspended before the personalities can respond
                         * by removing the device from the array (i.e. calling
                         * 'hot_remove_disk').  If they haven't yet removed
                         * the failed device, its 'raid_disk' number will be
                         * '>= 0' - meaning we must call this function
                         * ourselves.
                         */
                        if ((r->raid_disk >= 0) &&
                            (r->mddev->pers->hot_remove_disk(r->mddev, r) != 0))
                                /* Failed to revive this device, try next */
                                continue;

                        r->raid_disk = i;
                        r->saved_raid_disk = i;
                        flags = r->flags;
                        clear_bit(Faulty, &r->flags);
                        clear_bit(WriteErrorSeen, &r->flags);
                        clear_bit(In_sync, &r->flags);
                        if (r->mddev->pers->hot_add_disk(r->mddev, r)) {
                                r->raid_disk = -1;
                                r->saved_raid_disk = -1;
                                r->flags = flags;
                        } else {
                                r->recovery_offset = 0;
                                cleared_failed_devices |= 1 << i;
                        }
                }
        }
        if (cleared_failed_devices) {
                rdev_for_each(r, &rs->md) {
                        sb = page_address(r->sb_page);
                        failed_devices = le64_to_cpu(sb->failed_devices);
                        failed_devices &= ~cleared_failed_devices;
                        sb->failed_devices = cpu_to_le64(failed_devices);
                }
        }
}

static int __load_dirty_region_bitmap(struct raid_set *rs)
{
        int r = 0;

        /* Try loading the bitmap unless "raid0", which does not have one */
        if (!rs_is_raid0(rs) &&
            !test_and_set_bit(RT_FLAG_RS_BITMAP_LOADED, &rs->runtime_flags)) {
                r = bitmap_load(&rs->md);
                if (r)
                        DMERR("Failed to load bitmap");
        }

        return r;
}

/* Enforce updating all superblocks */
static void rs_update_sbs(struct raid_set *rs)
{
        struct mddev *mddev = &rs->md;
        int ro = mddev->ro;

        set_bit(MD_CHANGE_DEVS, &mddev->flags);
        mddev->ro = 0;
        md_update_sb(mddev, 1);
        mddev->ro = ro;
}

/*
 * Reshape changes raid algorithm of @rs to new one within personality
 * (e.g. raid6_zr -> raid6_nc), changes stripe size, adds/removes
 * disks from a raid set thus growing/shrinking it or resizes the set
 *
 * Call mddev_lock_nointr() before!
 */
static int rs_start_reshape(struct raid_set *rs)
{
        int r;
        struct mddev *mddev = &rs->md;
        struct md_personality *pers = mddev->pers;

        r = rs_setup_reshape(rs);
        if (r)
                return r;

        /* Need to be resumed to be able to start reshape, recovery is frozen until raid_resume() though */
        if (mddev->suspended)
                mddev_resume(mddev);

        /*
         * Check any reshape constraints enforced by the personalility
         *
         * May as well already kick the reshape off so that * pers->start_reshape() becomes optional.
         */
        r = pers->check_reshape(mddev);
        if (r) {
                rs->ti->error = "pers->check_reshape() failed";
                return r;
        }

        /*
         * Personality may not provide start reshape method in which
         * case check_reshape above has already covered everything
         */
        if (pers->start_reshape) {
                r = pers->start_reshape(mddev);
                if (r) {
                        rs->ti->error = "pers->start_reshape() failed";
                        return r;
                }
        }

        /* Suspend because a resume will happen in raid_resume() */
        if (!mddev->suspended)
                mddev_suspend(mddev);

        /*
         * Now reshape got set up, update superblocks to
         * reflect the fact so that a table reload will
         * access proper superblock content in the ctr.
         */
        rs_update_sbs(rs);

        return 0;
}

static int raid_preresume(struct dm_target *ti)
{
        int r;
        struct raid_set *rs = ti->private;
        struct mddev *mddev = &rs->md;

        /* This is a resume after a suspend of the set -> it's already started */
        if (test_and_set_bit(RT_FLAG_RS_PRERESUMED, &rs->runtime_flags))
                return 0;

        /*
         * The superblocks need to be updated on disk if the
         * array is new or new devices got added (thus zeroed
         * out by userspace) or __load_dirty_region_bitmap
         * will overwrite them in core with old data or fail.
         */
        if (test_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags))
                rs_update_sbs(rs);

        /*
         * Disable/enable discard support on raid set after any
         * conversion, because devices can have been added
         */
        configure_discard_support(rs);

        /* Load the bitmap from disk unless raid0 */
        r = __load_dirty_region_bitmap(rs);
        if (r)
                return r;

        /* Resize bitmap to adjust to changed region size (aka MD bitmap chunksize) */
        if (test_bit(RT_FLAG_RS_BITMAP_LOADED, &rs->runtime_flags) &&
            mddev->bitmap_info.chunksize != to_bytes(rs->requested_bitmap_chunk_sectors)) {
                r = bitmap_resize(mddev->bitmap, mddev->dev_sectors,
                                  to_bytes(rs->requested_bitmap_chunk_sectors), 0);
                if (r)
                        DMERR("Failed to resize bitmap");
        }

        /* Check for any resize/reshape on @rs and adjust/initiate */
        /* Be prepared for mddev_resume() in raid_resume() */
        set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
        if (mddev->recovery_cp && mddev->recovery_cp < MaxSector) {
                set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
                mddev->resync_min = mddev->recovery_cp;
        }

        rs_set_capacity(rs);

        /* Check for any reshape request unless new raid set */
        if (test_and_clear_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags)) {
                /* Initiate a reshape. */
                mddev_lock_nointr(mddev);
                r = rs_start_reshape(rs);
                mddev_unlock(mddev);
                if (r)
                        DMWARN("Failed to check/start reshape, continuing without change");
                r = 0;
        }

        return r;
}

static void raid_resume(struct dm_target *ti)
{
        struct raid_set *rs = ti->private;
        struct mddev *mddev = &rs->md;

        if (test_and_set_bit(RT_FLAG_RS_RESUMED, &rs->runtime_flags)) {
                /*
                 * A secondary resume while the device is active.
                 * Take this opportunity to check whether any failed
                 * devices are reachable again.
                 */
                attempt_restore_of_faulty_devices(rs);
        }

        mddev->ro = 0;
        mddev->in_sync = 0;

        clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

        if (mddev->suspended)
                mddev_resume(mddev);
}

static struct target_type raid_target = {
        .name = "raid",
        .version = {1, 9, 0},
        .module = THIS_MODULE,
        .ctr = raid_ctr,
        .dtr = raid_dtr,
        .map = raid_map,
        .status = raid_status,
        .message = raid_message,
        .iterate_devices = raid_iterate_devices,
        .io_hints = raid_io_hints,
        .presuspend = raid_presuspend,
        .postsuspend = raid_postsuspend,
        .preresume = raid_preresume,
        .resume = raid_resume,
};

static int __init dm_raid_init(void)
{
        DMINFO("Loading target version %u.%u.%u",
               raid_target.version[0],
               raid_target.version[1],
               raid_target.version[2]);
        return dm_register_target(&raid_target);
}

static void __exit dm_raid_exit(void)
{
        dm_unregister_target(&raid_target);
}

module_init(dm_raid_init);
module_exit(dm_raid_exit);

module_param(devices_handle_discard_safely, bool, 0644);
MODULE_PARM_DESC(devices_handle_discard_safely,
                 "Set to Y if all devices in each array reliably return zeroes on reads from discarded regions");

MODULE_DESCRIPTION(DM_NAME " raid0/1/10/4/5/6 target");
MODULE_ALIAS("dm-raid0");
MODULE_ALIAS("dm-raid1");
MODULE_ALIAS("dm-raid10");
MODULE_ALIAS("dm-raid4");
MODULE_ALIAS("dm-raid5");
MODULE_ALIAS("dm-raid6");
MODULE_AUTHOR("Neil Brown <dm-devel@redhat.com>");
MODULE_AUTHOR("Heinz Mauelshagen <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");